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Index to all Newsletters LMNO Engineering home page LMNO@LMNOeng.com |

2002

December 4, 2002. Water flowing from a tank

November 2, 2002. Natural Gas Flow

September 21, 2002. Pressurized Non-Circular
Ducts/Conduits

August 23, 2002. New Calculation - Bypass Loop

July 15, 2002. Flow in Bypass Loop

June 10, 2002. New Calculation - Small Bore Orifice
for Gas Flow

May 29, 2002. Open channel flow measurement - what device
to use

May 7, 2002. Backwater Calculator now on-line

April 16, 2002. Gradually Varied Flow Calculations

March 27, 2002. Gradually Varied Flow and Rapidly
Varied Flow

March 4, 2002. New small diameter orifice calculation.
Modeling closed piping loops

February 12, 2002. Small Diameter Orifice Flowmeter

January 15, 2002. New Calculation - Inverted Siphon
(Depressed Sewer)

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, OH 45701 USA (740) 592-1890

LMNO@LMNOeng.com

Newsletter. December 4, 2002

Water flowing from a tank

One of our users inquired about how to increase the discharge from a tank by pressurizing
the head space above the water in the tank. He was using the Discharge from a Tank
calculation ( http://www.LMNOeng.com/TankDischarge.htm
).

Since the calculation assumes the top of the tank is open to the atmosphere, how do you
account for the additional tank pressure? Let's look at the free discharging orifice (as
opposed to the submerged orifice). H is the distance shown in the figure on the
calculation page. The equation to use is H=h_{1}+h_{1}. Let h_{1}
be the depth of water above the orifice. Let h_{2}=P/S where P is the head
pressure (gage pressure; not absolute pressure) in the tank and S is the weight density of
the water in the tank (also known as specific weight). If P=0, then H=h_{1} as
expected for a tank open to the atmosphere.

Let's look at an example. If h_{1}=3 ft. and P=5 psig (pounds per square inch,
gage pressure), then h_{2} = (5 lb/in^{2})(144 in^{2}/ft^{2})/(62.3
lb/ft^{3})=11.6 ft. 62.3 is S for water at 70 F. If your water has a different
temperature, use S for your temperature (but it won't be very different). Therefore, H=3 +
11.6 = 14.6 ft. You can also use the calculation backwards: Enter the discharge that you
need and the calculation will compute H. Then, determine P based on your h_{1}.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com .

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, OH 45701 USA (740) 592-1890

LMNO@LMNOeng.com

Newsletter. November 2, 2002

Natural Gas Flow

Recently, LMNO Engineering has been consulting for the natural gas industry. The LMNO
Engineering website currently doesn't have any calculations specifically for natural gas.
We have calculations using the Darcy-Weisbach method which can analyze gases so long as
gas compressibility is minimal for the pipe run.

Crane TP-410 provides several equations specifically developed for natural gas flow. They
are the Spitzglass, Weymouth, and Panhandle formulas. All three formulas are empirical.
The Spitzglass formula is valid for low pressure gas having less than 1 psig pressure (69
mbar gage). Weymouth is valid for high pressure gas, and the Panhandle is valid for 6 to
24 inch (15 to 60 cm) gas lines with Reynolds numbers between 5 million and 14 million.

We receive quite a few e-mail questions about natural gas and are considering developing
calculations using the Spitzglass, Weymouth, and Panhandle equations. I am interested in
any feedback you might have about whether these calculations would be helpful to you.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

Reference:

Crane Co. Flow of fluids through valves, fittings, and pipe. Technical Paper 410 (TP 410).
1988.

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid mechanics calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, OH 45701 USA (740) 592-1890

LMNO@LMNOeng.com

Newsletter. September 21, 2002

Pressurized Non-Circular Ducts/Conduits

Recently, we have been receiving a lot of inquiries asking how to model non-circular
pressurized conduits. Our free calculation titled "Non-Circular to Circular Pipe
Conversions" at http://www.LMNOeng.com/PipeDuct.htm
will help. The calculation allows one to use the circular pipe design calculations
("Design of Circular Water Pipes" and "Design of Circular Liquid and Gas
Pipes") for non-circular cross-sections.

If you have a rectangular or annular cross-section, the non-circular calculation will
convert your geometry to an equivalent diameter (called hydraulic diameter) which can then
be used in the circular design calculations to predict velocity. However, to calculate the
flowrate, take the velocity from the design calculation page and copy it to the
non-circular calculation page so that the velocity is multiplied by the actual duct area.
This will give the correct flowrate. The flowrate output in the circular design
calculation is computed as VA where A=(pi/4)D^{2}, which is incorrect for a
non-circular cross-section. Even though the D is the hydraulic diameter, (pi/4)D^{2}
is not equal to the area computed from the actual duct geometry. Type some sample numbers
in the non-circular calculation to prove it to yourself, then compare the calculation's
area to (pi/4)D^{2} using your calculator.

Conversely, if you use "Design of Circular Water Pipes" to determine a pipe
diameter based on a required velocity, the non-circular calculation can be used to convert
the diameter to a height and width of a rectangular duct or an inner and outer diameter
for an annular cross-section. For the same reasons as in the previous paragraph, the
circular pipe design calculations cannot be used to compute hydraulic diameter based on
flowrate, since A=(pi/4)D^{2} is used.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. August 23, 2002.

New Calculation - Bypass Loop

http://www.LMNOeng.com/Pipes/bypass.htm

Our bypass calculation is now complete. My last newsletter provided an example of how to use it for design. The calculation has three options: 1) It will size a pump in the bypass loop to draw fluid from the main pipe into the loop, 2) It will size a pump in the main pipe that forces fluid into the bypass loop, or 3) It will determine the length of a contraction in the main pipe so that fluid is forced into the loop.

The calculation has a demonstration mode for mercury flowing through wooden pipes. It's not a very useful fluid or pipe material for most people but shows the functionality of the calculation for free. Other fluids and pipe materials are selectable from the drop-down menus, but require paid registration to enable the Calculate button. As with our other calculations, you can select from a wide variety of units using the drop-down menus.

We hope the calculation is useful to you. Thank you for your interest in the LMNO
Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com .

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. July 15, 2002.

Flow in Bypass Loop

Let's say you have an 8 inch (20 cm) diameter water pipe flowing at 300 gpm (US gpm or 19
liter/s). For some reason you need to bypass 0.5 gpm (0.03 liter/s) of the water through a
0.5 inch (1.3 cm) diameter loop that is 5 ft. (1.5 m) long. How do you get the water to
flow from the 8 inch diameter main pipe into the bypass loop at the desired rate of 0.5
gpm?

There are different ways to achieve the 0.5 gpm in the bypass loop. You could install an
orifice, valve or other type of flow restriction in the main pipe between the bypass
take-off and return. The flow restriction will increase the loss (pressure difference)
across the restriction encouraging water to flow through the bypass loop. Another option
would be to install a pump in the bypass loop which would draw water from the main pipe
into the bypass loop. As another alternative, if you already have a pump in the main line
- and the location of the bypass loop is adaptable - then the bypass take-off could be at
the discharge side of the pump and the bypass return could be to the inlet side of the
pump.

As a note of caution: Most methods used to achieve a desired flowrate through the bypass
loop will cause a reduction of flow in the main pipe.

We are currently developing a calculation that will help you determine the best way to
achieve a desired flowrate through a bypass loop. The calculation will be valid for both
liquids and gases. It will enable you to investigate sizing a restriction in the main
pipe, sizing a pump in the bypass loop, or locating the bypass loop across a pump in the
main pipe.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. June 10, 2002.

New Calculation - Small Bore Orifice for Gas Flow

http://www.LMNOeng.com/Flow/SmallOrificeGas.htm

You asked for it! We wrote it! A calculation for gas flow through a small bore orifice.
The calculation will compute flowrate, differential pressure, or bore diameter for gas
flow through an orifice installed in a pipe having a diameter between 0.64 cm and 5 cm.

Our calculation is based on the equations and methodology described in ASME MFC-14M-2001.
You may select flange taps or corner taps. The method is valid for pipe Reynolds numbers
greater than 1000 and diameter ratios between 0.1 and 0.8 for corner taps (0.15 and 0.7
for flange taps).

As with all of our calculations, a variety of units are selectable from drop-down menus.
Fluid properties are built-in for air, methane, nitrogen, oxygen, carbon dioxide, and
other gases. Alternatively, you may enter properties for gases not listed.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

Reference:

American Society of Mechanical Engineers (ASME). 2001. Measurement of fluid flow using
small bore precision orifice meters. ASME MFC-14M-2001.

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm.

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. May 29, 2002.

Open channel flow measurement - what device to use

Maybe you need to determine the discharge (flowrate) in an open channel. How should you do
it? There are many methods depending on your situation.

If the water is discharging freely out of a horizontal culvert, you can measure the
culvert diameter and either the depth or the top width of the water. Then use the end
depth method http://www.LMNOeng.com/Waterfall/CulvertDischarge.htm
to determine the discharge.

Or, if the discharge out of the culvert is not too high, you can hold a bucket under the
water and measure the time required to fill the bucket. Then, compute the discharge by
dividing the bucket volume by the fill time.

If you need to determine the discharge in a channel, a weir or flume could be installed. A
weir will cause the water to back up behind the weir. Then, the water depth upstream of
the weir is directly related to the discharge. See http://www.LMNOeng.com/Weirs/vweir.htm.
Alternatively, a flume could be installed. The water won't back up nearly as much behind a
flume, but they are more expensive to make. The water depth at the throat of the flume is
related to the discharge. See http://www.LMNOeng.com/Flumes/flumes.htm.

A cheaper way to determine discharge in an open channel is simply to drop a cork into the
channel and record the time required for it to travel a certain distance. The stream
velocity is computed from distance divided by time. Then, if you can determine the
stream's cross-sectional area, the discharge equals velocity times area. This method may
not be very accurate since it is often difficult to determine the area of a stream, and
the stream area is often not constant. Further, the velocity measured is the velocity of
the water surface which tends to be higher than the stream's average velocity.

I hope I have provided some helpful ideas for measuring discharge in open channels. Thank
you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm.

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. May 7, 2002.

Backwater Calculator now on-line

http://www.LMNOeng.com/Channels/gvf.htm

Please take a look at our newest calculation http://www.LMNOeng.com/Channels/gvf.htm.
It has a nice demonstration mode, so you can see many graphs showing water depth upstream
or downstream of a barrier. It will also plot velocity, Froude number, and top width
versus distance in the demonstration mode. In addition to the graph, numbers for depth,
velocity, Froude number, etc. are output at any distance specified by the user.

Using the default numbers in the calculation, press "Calculate" to see a graph
of water surface and channel invert elevations. The graph shows that the water surface
eventually parallels the channel invert. This happens because, as you go further and
further upstream of the dam, the water seeks the normal depth. Normal depth is also known
as the uniform flow depth. Invert is the channel bottom.

The calculation is very helpful for determining whether an existing channel will overflow
during a flood, or for designing a channel to contain floodwaters. As usual, the
calculation allows many different units.

Since this is our third newsletter in a row on gradually varied flow, I will write about a
different topic next time. If you have any ideas for newsletter topics, please let me
know.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com LMNO@LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. April 16, 2002.

Gradually Varied Flow Calculations

My last newsletter discussed gradually varied flow (GVF) and rapidly varied flow (RVF). As
a quick review, GVF and RVF are terms used to classify open channel flows - such as flow
in rivers, canals, and culverts. RVF occurs over short distances such as when water flows
over a weir or dam, drops off the end of a pipe, or encounters an hydraulic jump. GVF
occurs over long distances such as the water approaching a weir, dam, or drop-off; or
following a sluice gate.

Since we will soon have a GVF calculation on our website, I am discussing GVF calculations
today. A GVF calculation first requires computation of the normal and critical depths (Y_{n}
and Y_{c}). If the discharge, channel slope, channel material, and channel
dimensions (except water depth) are known, then Yn can be computed using Manning's
equation. Yn is also known as the uniform flow depth. It is the depth that water seeks in
a long channel. Yc is computed by setting the Froude number to 1.0 and solving for depth.
Please see http://www.LMNOeng.com/Channels/trapezoid.htm
for normal and critical depth equations and computations. If Yn is greater than, equal to,
or less than Yc, then the channel has a mild slope, critical slope, or steep slope,
respectively.

To perform a GVF calculation, you need to know the water depth at some location in your
channel (call this Ys, for start depth). For example, maybe you know the water depth
behind a dam at a certain discharge - such as 10 m at 30 cms (cubic meters per second).
Or, maybe you know the water depth under a sluice gate at a certain discharge. If the
channel slope is mild and Ys is greater than Yc, then the channel has downstream control
and the GVF calculation proceeds upstream. If the slope is steep and Ys is less than Yc,
then the channel has upstream control and the GVF calculation proceeds downstream. The GVF
computation then provides the water depth profile in the channel upstream or downstream of
Ys, depending on whether or not there is downstream or upstream control.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. March 27, 2002.

Gradually Varied Flow (GVF) and Rapidly Varied Flow (RVF)

GVF and RVF are terms used to classify open channel flows - such as flow in rivers,
canals, and culverts. RVF occurs over short distances such as when water flows over a weir
or dam, drops off the end of a pipe, or encounters an hydraulic jump. GVF occurs over long
distances such as the water approaching a weir, dam, or drop-off; or following a sluice
gate.

In long prismatic (constant cross-section geometry) channels, the water will attempt to
reach the "normal depth". Normal depth is the water depth determined using
Manning's equation (or Chezy's equation). How the water depth changes with distance as it
approaches its normal depth is called a GVF profile. A GVF profile is a computation of
water depth versus distance along the channel length. A GVF computation typically involves
starting at a known depth (e.g. at a dam) and making successive computations upstream
using the continuity equation and energy slope in Manning's equation (rather than using
the channel bottom slope). It is a numerical computation and for best accuracy you want to
use the smallest distance increments possible. If you have had a course in open channel
flow, you might recall the different GVF profile types - such as M1, M2, M3, S1, S2, S3,
etc. I'll leave discussion of these to another newsletter!

RVF computations require the continuity equation and the energy equation (like Bernoulli
equation but with losses) and/or momentum equation. To analyze an hydraulic jump,
continuity and momentum are required. To analyze flow over a dam/weir, continuity and
energy are used. Often, empirical methods are used to analyze flow over weirs.

I discussed gradually and rapidly varied flows in this newsletter because we will soon
complete a GVF computation for trapezoidal channels.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. March 4, 2002

Two topics in today's newsletter:

1) New small diameter orifice calculation

2) Modeling closed piping loops

Usually I don't try to have two different topics in the same newsletter, but I wanted to
let you know that the small diameter orifice calculation for liquids that I mentioned in
my last newsletter is now on our site at http://www.LMNOeng.com/Flow/SmallOrificeLiq.htm.

On a separate topic, today I received a phone call from someone inquiring about how to
model a closed pipe loop containing a pump. I think there might be general interest in
modeling closed loops, so I'm going to discuss it. Let's simplify the system and say we
have a pump followed by 300 ft of 4 inch diameter pipe which goes up to a height of 50 ft,
winds around awhile, then goes back down to the pump. He wanted to know the pump head
required to deliver a certain flowrate.

This loop system can be modeled using http://www.LMNOeng.com/DarcyWeisbach.htm
and setting the elevation difference (Z_{1}-Z_{2}) and the pressure
difference (P_{1}-P_{2}) both to 0.0. Then, select Scenario A (pipe only)
and "Q known, Solve for Pump Head". My friend on the phone was surprised that I
told him to set the elevation and pressure differences to 0.0. However, setting them to
0.0 is correct since it is a closed loop: the pipe goes up after the pump but comes back
down before going back into the pump, so all elevation changes cancel each other out.
Likewise, the high pressure at the discharge side of the pump is lost as the fluid (water,
gas, whatever) moves through the piping system, but is entirely gained back after going
through the pump.

The losses in the system - due to pipe friction, valves, bends, contractions, expansions,
etc. - combine to form the total dynamic head (pump head) that the pump must overcome.

I hope today's topic was helpful. Thank you for your interest in the LMNO Engineering
newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter4.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. February 12, 2002

Small Diameter Orifice Flowmeter

Many website visitors have asked if we have a calculation for orifice flowmeters having
pipe diameters less than 2 inch (5 cm). Our current orifice meter calculations are valid
only for pipes having at least 2 inch diameters:

http://www.LMNOeng.com/orifice.htm
(liquid flow, > 2 inch pipe diameter)

http://www.LMNOeng.com/Flow/OrificeGas.htm
(gas flow, > 2 inch pipe diameter)

In the past for pipes having less than 2 inch diameters, we have suggested our Bernoulli
calculation which uses a fixed value for the discharge coefficient and therefore is not as
accurate as an orifice calculation based on a standard methodology such as ISO or ASME.
The ISO and ASME standards are developed from the results of many experiments conducted at
various locations over a period of many years or decades. The discharge coefficient
correlations in the standards are often complex - being functions of diameters, Reynolds
numbers, and empirical constants.

Due to your requests, we have been working on a small diameter orifice calculation for
liquids, and it will be finished for our next newsletter. It will be based on ASME
MFC-14M-2001, "Measurement of fluid flow using small bore precision orifice
meters." We are also working on a small diameter orifice gas flow calculation which
accounts for the expansibility of a gas as it accelerates through the orifice - based on
the same ASME standard.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com

ISO is the International Organization of Standards

ASME is the American Society of Mechanical Engineers

Our Bernoulli calculation can be found at http://www.LMNOeng.com/Flow/bernoulli.htm

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter3.htm

You received this free newsletter because you requested it at our website. If you no
longer wish to receive it, send a message stating "Discontinue Newsletter" to LMNO@LMNOeng.com.

(c) 2002 LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.

The fluid flow calculations website: http://www.LMNOeng.com

7860 Angel Ridge Rd. Athens, Ohio 45701 USA +1(740) 592-1890

LMNO@LMNOeng.com

Newsletter. January 15, 2002

New Calculation - Inverted Siphon (Depressed Sewer)

http://www.LMNOeng.com/Channels/InvertedSiphon.htm

My last newsletter discussed the concept of the inverted siphon - it is used to allow
sewers to pass under obstructions such as rivers, subways, other piping systems, etc. We
have now completed our inverted siphon calculation.

The calculation will determine the diameters of up to 5 siphons. The calculation will also
work in reverse - you enter the diameters, and the flowrates are computed.

In all cases, the user enters the diameter, slope, and roughness coefficient for the main
sewer pipe. Our calculation computes the discharge through the main sewer under design
conditions (flowing full) using the Manning equation. The user also enters the elevation
difference between the inlet and outlet junction chambers. The junction chambers are where
the main sewer pipe branches into the siphon pipes and where the siphon pipes then merge
back into the main sewer pipe after passing the obstruction.

The user also enters the siphon length and Manning roughness coefficient for the siphon
pipes since they may be of different material than the sewer main. The hydraulic grade
line of the siphon is computed as the elevation drop divided by the siphon length. Unlike
the sewer main, the siphon pipes are designed to flow under pressure.

The calculation then computes siphon diameters, inlet invert elevations, wall heights in
the inlet chamber (to allow for splitting of the main sewer flow into the various
siphons), and velocity through each siphon.

We hope the calculation is useful to those of you in the civil engineering public works
discipline. We wrote it due to the large number of requests for this type of calculation.
The calculation can be found at http://www.LMNOeng.com/Channels/InvertedSiphon.htm.

Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)

LMNO Engineering, Research, and Software, Ltd.

http://www.LMNOeng.com

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter3.htm

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