Flow in Open Channels
Flow in an open channel on a slope occurs due to the effect of gravity on the liquid. In many cases the flow of liquid has a free surface, as in a open channel, flume or only partially full pipe. The liquid is under no pressure, other than atmospheric pressure. Over time, a number of formulae have been developed to provide an estimate of the flow rate that will occur in open-channels, with the Manning formula becoming widely accepted as the usual and best method of obtaining a reliable estimate of the flow.
Flow in Part Full Pipes
The Manning coefficient is used in the Manning formula to correct for the type of channel under consideration. The cross-sectional area of the flow, the wetted perimeter and the slope ratio must be calculated. The results are more accurate if the cross-section of flowing fluid, the fluid velocity, depth of fluid and the slope are constant (steady flow). The resulting flow rate estimates are applicable to water or fluids with similar properties to water.
Flow from Tanks and Tank Emptying Time
The flow rate from a tank outlet will be dependant on the head of fluid above the outlet position and the type and size of the orifice that the fluid exits through. The outlet pipe itself will also affect the flow rate, as it will introduce additional friction losses, unless it is relatively short.
As fluid exits the tank, the level of fluid remaining in the tank will decrease and thus the fluid head available to 'push' liquid out of the tank decreases over time, which in turn reduces the outlet flow rate over time. The shape of the tank also affects the tank emptying time, since for a given volume of flow out of the tank, the height of fluid lost from the tank will be different for different shapes of tank.
OPEN CHANNEL FLOW AND PART FILLED PIPES
Open-channel flow occurs when a liquid flows due to gravity. Usually the flowing liquid has a free surface, as in a channel, flume or partially full pipe. The liquid is not under pressure, other than atmospheric pressure. Many formulae have been developed to estimate the flow rate in open-channels, the Manning formula has become widely accepted as the usual method of estimating flow rate.
WATER FLOW RATE CALCULATION
The Manning formula uses a coefficient to correct for the type of channel in use. The cross-sectional area of the flow, the wetted perimeter of the flow and the slope ratio must be calculated. The results are more accurate if the flow cross-section, velocity, depth and slope are constant (steady flow). The flow rate estimates are applicable to water or fluids similar to water.
TIME TAKEN TO EMPTY TANKS
The flow rate from a tank outlet will be dependant on the orifice size, orifice type and the head of fluid above the outlet position. The addition of an oulet pipe may restrict the oulet flow rate unless the outlet pipe is relatively short. As the tank empties the fluid head will reduce progressively, reducing the outlet flow rate. The shape of the tank will also affect the time taken to empty, as changes in shape will affect the rate of change of the fluid head available.
VOLUME, CAPACITY, WEIGHT & EXPANSION
The inner volume, fluid capacity, weight and expansion of various pipes, sections, channels and tanks can be calculated. The weight of a pipe, channel or tank in various material constructions (steel, wood, aluminium, brass etc.) and the fluid contents may be displayed by entering the appropriate dimensions and choosing the material and fluid type.
Thanks for reading Pipe Flow Advisor. Please share...!
0 Comment for "Pipe Flow Advisor"