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fluid speed vs pressure 2
- Thread starter Hagar1
- Start date
sailoday28
Mechanical
venkatParam
You did not specify if the fluid was compressible.
My response was for a highly incompressible fluid-such as a liquid.
However, if the fluid is compressible, then the approach to solve the pressure-velcity distribution should be done with the method of characteristics (MOC) approach.
And that would be an interesting topic for this forum to explore.
You did not specify if the fluid was compressible.
My response was for a highly incompressible fluid-such as a liquid.
However, if the fluid is compressible, then the approach to solve the pressure-velcity distribution should be done with the method of characteristics (MOC) approach.
And that would be an interesting topic for this forum to explore.
venkatParam
Mechanical
Thank You guys,
The fluid is incompressible. And frinctional losses are negligible. And I still have some questions. If a flow of low velocity nothing compared to that of sound etc, is stopped in its path. Based on Bernoulli's law,
The stagnation pressure = Static pressure + (rho*V*V)/(2)
So shouldn't the force = area * Stagnation Pressure
Based on
"This pressure must be added to the prevailing static pressure to verify that the pipe is not subjected to excessive tensile stresses" by 25362
25362 : According to you F = (?)(q)(v)/g
Dimensionally speaking
(F)is force (Kg m/s2)
(?)is density(Kg/m3)
(q)is ? (m4/s3) What is this term
(v)is velocity (m/s)
(g)is 9.8 (m/s2)
Also, is the static pressure term (P/?) in the equation, depending on the source or is constant in an environment etc.
Sorry guys if i sound too confused but i am.
I am trying to simulate this flow using FEMLAB.
Thank you for your time
The fluid is incompressible. And frinctional losses are negligible. And I still have some questions. If a flow of low velocity nothing compared to that of sound etc, is stopped in its path. Based on Bernoulli's law,
The stagnation pressure = Static pressure + (rho*V*V)/(2)
So shouldn't the force = area * Stagnation Pressure
Based on
"This pressure must be added to the prevailing static pressure to verify that the pipe is not subjected to excessive tensile stresses" by 25362
25362 : According to you F = (?)(q)(v)/g
Dimensionally speaking
(F)is force (Kg m/s2)
(?)is density(Kg/m3)
(q)is ? (m4/s3) What is this term
(v)is velocity (m/s)
(g)is 9.8 (m/s2)
Also, is the static pressure term (P/?) in the equation, depending on the source or is constant in an environment etc.
Sorry guys if i sound too confused but i am.
I am trying to simulate this flow using FEMLAB.
Thank you for your time
sailoday28
Mechanical
Bernoulli's equation is for steady state flow.
IT IS NOT APPLICABLE TO :
Stopping the flow as related to sudden or changing the flow velocity.
Now at a point in steady state flow where the velcity is zero, one may apply stagnation properties to determine pressure.
IT IS NOT APPLICABLE TO :
Stopping the flow as related to sudden or changing the flow velocity.
Now at a point in steady state flow where the velcity is zero, one may apply stagnation properties to determine pressure.
To venkatParam. You are absolutely right.
q is flow rate, for example, m3/s.
Force can be expressed in various manners. For example kgf = 9.8 N = 9.8 kg.m/s2.
Thus, (kg/m3)(m3/s)(m/s) = kg.m/s2.
Dividing by 9.8 one gets kgf. I should have said that g is a constant = 9.8, and call it gc to distinguish it from the acceleration of gravity 9.8 m/s2.
Otherwise one gets kg which is a measure of mass, not a force.
Another way to express the perpendicular impact force would be [ρ]Av2. By dimensions:
(kg/m3)(m2)(m/s)2 = kg.m/s2, which has the dimensions of force, as given by mass times acceleration.
q is flow rate, for example, m3/s.
Force can be expressed in various manners. For example kgf = 9.8 N = 9.8 kg.m/s2.
Thus, (kg/m3)(m3/s)(m/s) = kg.m/s2.
Dividing by 9.8 one gets kgf. I should have said that g is a constant = 9.8, and call it gc to distinguish it from the acceleration of gravity 9.8 m/s2.
Otherwise one gets kg which is a measure of mass, not a force.
Another way to express the perpendicular impact force would be [ρ]Av2. By dimensions:
(kg/m3)(m2)(m/s)2 = kg.m/s2, which has the dimensions of force, as given by mass times acceleration.
sailoday28
Mechanical
25362 (Chemical)states
Another way to express the perpendicular impact force would be ?Av2.
Please note-- for THIS steady state problem the force is related to the change in MOMENTUM. AND therfore for flow perpendicular to a surface one may use the incoming velocity AS the incoming momentum---AND the exit momentum is ZERO. The force from the net change in momentum in the icoming direction is as '25362 (Chemical)states'
I reiterate, if the FLOW, (not an individual path line) is suddenly changed, then the "water hammer" type equation must be used to detrmine pressure, velocity, force distribution.
Another way to express the perpendicular impact force would be ?Av2.
Please note-- for THIS steady state problem the force is related to the change in MOMENTUM. AND therfore for flow perpendicular to a surface one may use the incoming velocity AS the incoming momentum---AND the exit momentum is ZERO. The force from the net change in momentum in the icoming direction is as '25362 (Chemical)states'
I reiterate, if the FLOW, (not an individual path line) is suddenly changed, then the "water hammer" type equation must be used to detrmine pressure, velocity, force distribution.
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