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2020

LMNO Engineering, Research, and Software, Ltd.

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2020
January 2, 2020. Focus on Hydrology - Impact of Culvert Replacement
January 22, 2020. Open Channel Uniform and Non-Uniform Flow
February 19, 2020. Gas Leak Rate Calculator - New
May 6, 2020. Calculators


LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, Ohio 45701 USA   (740) 707-2614
LMNO@LMNOeng.com

Newsletter. January 2, 2020.

Focus on Hydrology - Impact of Culvert Replacement

We recently completed a culvert design consulting project. Culvert design is a mature field, so it would seem that most of the nuances have been worked out. However, sometimes the impacts of culvert replacement are overlooked. A culvert may be replaced due to its having been partially crushed or having deteriorated so that it no longer properly conveys the intended design flow at the original design upstream head (water depth). It is tempting to simply replace the culvert with the same or larger size. While this is usually the strategy, it can have unintended downstream consequences.

Replacing a culvert with the same or larger diameter, and clearing brush/debris, results in less flow resistance - which is a desirable consequence. However, the failed culvert may have provided stormwater detention upstream of the culvert. Upon replacement, there is less flow resistance resulting in less upstream stormwater detention and an increased risk of downstream flooding.

Please let me know if questions. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://www.LMNOeng.com     LMNO@LMNOeng.com

Culvert design calculator: https://www.LMNOeng.com/Pipes/hds.php


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.

© 2020 LMNO Engineering, Research, and Software, Ltd.


LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, Ohio 45701 USA   (740) 707-2614
LMNO@LMNOeng.com

Newsletter. January 22, 2020.

Open Channel Uniform and Non-Uniform Flow

The empirical Manning equation is the most commonly used equation for open channel flows. In open channel flow, the water surface is open to the atmosphere. For instance, open channel flow can be in a partially full pipe, in a natural stream or river, or in a manmade channel. The Manning equation is of the form:

Q = A k R2/3 S1/2 / n

where: Q = Flow rate (m3/s or ft3/s). A = Cross-sectional flow area (m2 or ft2). k = Unit conversion factor = 1 for SI units or 1.49 for English units. R = Hydraulic Radius (m or ft) = A/P, where P = Wetted perimeter (m or ft). S = Energy slope = Change in water surface elevation per unit length of channel (m/m or ft/ft). n = Manning roughness factor.

If the channel or pipe that water is flowing through is long with unchanging dimensions (a "prismatic" channel), then the water depth will be nearly constant along the channel's length. This situation is called uniform flow; the water surface is modeled as being parallel to the channel bottom. In this case, the slope of the channel can be used as the energy slope S. However, if the channel is not prismatic or the water depth changes with distance (near a channel drop-off for instance), then the energy slope S is the slope of the water surface, rather than the slope of the channel.

In many instances, we know the flow rate in the channel and need to determine the water depth. In this case, the Manning equation is solved for water depth numerically since S, A, and P (thus R) are functions of the water depth. If flow is uniform, then water depth is constant along the entire channel, so the Manning equation only needs to be solved numerically once for depth. If the water depth varies along the channel length (non-uniform flow), then the Manning equation is solved numerically for water depth, not just once, but over and over at small distance increments successively moving upstream or downstream along the channel.

More information can be found on our web pages: Uniform flow in pipe: https://www.LMNOeng.com/CircularCulvert.php
Uniform flow in trapezoidal channel: https://www.LMNOeng.com/Channels/trapezoid.php
Non-uniform flow in trapezoidal channel: https://www.LMNOeng.com/Channels/gvf.php (has demo mode and graph; note that non-uniform flow is also called gradually varied flow)

Please let me know if questions. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://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.

© 2020 LMNO Engineering, Research, and Software, Ltd.


LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, Ohio 45701 USA   (740) 707-2614
LMNO@LMNOeng.com

Newsletter. February 19, 2020.

New calculator - Gas Leak Rate
https://www.LMNOeng.com/Gas/GasLeakRate.php

Gas can intentionally or unintentionally be vented from a tank or pipe to the surrounding air. The gas venting may occur through an orifice, crack, or other opening. Depending on the type of gas, temperature, and pressures, the gas flow may either be choked or subsonic as it exits through the hole. If flow is choked, the gas exits the tank at sonic velocity (Mach number of 1). If flow is subsonic, then the discharge Mach number is less than 1. As gas leaks through the crack, temperature drops. If the gas contains water vapor, then there is a possibility of freezing of entrained liquid.

In the calculator, you can select the type of gas or enter the specific gravity (or molecular weight) and specific heat ratio. Other inputs include tank pressure, tank temperature, ambient pressure, and hole size. The calculation is for steady state conditions. The computed values include mass flow rate, velocity through the hole, Mach number, and temperature.

Please let me know if questions. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://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.

© 2020 LMNO Engineering, Research, and Software, Ltd.


LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, Ohio 45701 USA   (740) 707-2614
LMNO@LMNOeng.com

Newsletter. May 6, 2020.

Calculators

As you know, we offer calculators for pressurized pipe flow, open channel flow, hydrology, and groundwater. Our list of calculators can be found at https://www.LMNOeng.com

Our pressurized pipe flow calculations are for liquid or gas flow. For compressible gases, we solve the Weymouth equation for pipelines and also compute leak rates and consider choked flow. We also offer a pipe network calculation for liquids, water hammer calculations, and pressure relief valve sizing. In addition, we have design calculators for orifice, nozzle, and venturi flow meters. We also have a fire hydrant residual pressure calculation, time to empty a liquid tank, and a general Bernoulli equation calculator.

For open channel flow, we have calculators for circular culverts and trapezoidal channel analysis. In addition, we offer a calculator for inlet and outlet control for culvert sizing. A gradually varied flow calculator computes water depth in a trapezoidal channel for subcritical and supercritical flows. Our inverted siphon calculator sizes pipes for going under rivers, highways, or other obstacles. We also have flow measurement calculators for flumes and weirs.

Regarding hydrology, we have calculators for rainfall-runoff, time of concentration, and storage basin sizing.

Our groundwater calculators compute flow through a permeameter, groundwater flow direction based on well head readings, and solve contaminant transport equations.

We also have calculators to determine the volume of a partially full inclined cylinder, riprap sizing, drag force, gas flow conversions between standard and actual, ideal gas, and gas viscosity as a function of temperature.

We also offer consulting services. If you have any questions, please let me know. Thank you for your interest in the LMNO Engineering newsletter,

Ken Edwards, Ph.D., P.E. (Owner/Engineer)
LMNO Engineering, Research, and Software, Ltd.
https://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.

© 2020 LMNO Engineering, Research, and Software, Ltd.


© 2020 LMNO Engineering, Research, and Software, Ltd. (All Rights Reserved)

LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd.   Athens, Ohio  USA   +1(740) 707-2614
LMNO@LMNOeng.com    https://www.LMNOeng.com