How water flows even after adverse pressure gradient?

In summary, the presence of a gradient is necessary for fluid flow, whether it is in the form of temperature or pressure differences. In the case of a Venturimeter, the flow is able to happen against an adverse pressure gradient due to the fluid's momentum. This is similar to a ball rolling uphill against gravity.
  • #1
Ravi Singh choudhary
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In nature, gradient is always required for flow; whether it is temperature gradient for heat transfer or pressure difference for fluid flow. There is a case of Venturimeter in which we have throat section. After throat there is a divergent section. How could flow even happen in that adverse pressure gradient?

Someone says it is due to energy gradient. That means we should not speak due to pressure gradient fluid flows.
 
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  • #2
Ravi Singh choudhary said:
In nature, gradient is always required for flow; whether it is temperature gradient for heat transfer or pressure difference for fluid flow. There is a case of Venturimeter in which we have throat section. After throat there is a divergent section. How could flow even happen in that adverse pressure gradient?

Someone says it is due to energy gradient. That means we should not speak due to pressure gradient fluid flows.
The fluid has momentum, and higher pressure downstream compared to upstream enables the flow to slow down. So, when fluid momentum (kinetic energy) is significant, you can have flow against an adverse pressure gradient.
 
  • #3
So What is the prerequisite for fluid flow?
 
  • #4
Ravi Singh choudhary said:
So What is the prerequisite for fluid flow?
Why do you need to have a prerequisite for fluid flow? That will depend on the specific physical situation. If you wish to identify some specific physical situations and as whether the fluid will be flowing through them, we can analyze that.
 
  • #5
1st case: Fluid is flowing due to gravity only as in case of open channel. There is no pressure difference I think.

2nd case:Fluid is being pumped to the top using centrifugal pump; so creating pressure difference using pump so that fluid flow is happening.

In the second case consider a venturi section in the vertical pipe. Fluid will flow because of net pressure difference between source and the sink. What I am thinking is that localized adverse pressure gradient is not able to reverse the momentum of the fluid. Similarly venturimeter is the instrument placed in a pipeline is not able to do the same.
 
  • #6
Ravi Singh choudhary said:
1st case: Fluid is flowing due to gravity only as in case of open channel. There is no pressure difference I think.
You have a gravitational force acting on the fluid, so if, if viscous resistance is negligible, the fluid velocity can accelerate downward just as with a body in free fall. If substantial viscous resistance is present, this balances the gravitational force by viscous shear, but only if the fluid is flowing. So the fluid has to flow to balance the gravitational force.
2nd case:Fluid is being pumped to the top using centrifugal pump; so creating pressure difference using pump so that fluid flow is happening.

In the second case consider a venturi section in the vertical pipe. Fluid will flow because of net pressure difference between source and the sink. What I am thinking is that localized adverse pressure gradient is not able to reverse the momentum of the fluid. Similarly venturimeter is the instrument placed in a pipeline is not able to do the same.
Yes and yes.
 
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  • #7
Not a direct answer to your question but you should enjoy this video of water flowing uphill :



Severn Bore
 
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  • #8
Pressure gradients result in a net force on fluid elements. If the fluid is already moving (e.g. due to some force previously exerted on it) then encountering an adverse pressure gradient will slow that fluid down. You might think of it as a ball rolling up a hill. If it has enough momentum then it will make it up the hill against gravity but will be much slower for the effort. This is essentially the same as a fluid moving against a pressure gradient.
 
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  • #9
Perfect explanation for me. Thanks a lot.
 

1. How does water flow against an adverse pressure gradient?

Water is able to flow against an adverse pressure gradient due to the cohesive and adhesive properties of water molecules. These properties allow water molecules to stick together and to other surfaces, creating a continuous flow even when facing resistance from an adverse pressure gradient.

2. What determines the direction and speed of water flow in an adverse pressure gradient?

The direction and speed of water flow in an adverse pressure gradient is determined by the magnitude of the pressure gradient and the viscosity of the fluid. A higher pressure gradient or lower viscosity will result in a faster flow, while a lower pressure gradient or higher viscosity will result in a slower flow.

3. How does the shape of an object affect water flow in an adverse pressure gradient?

The shape of an object can affect water flow in an adverse pressure gradient by creating areas of high and low pressure. For example, an object with a curved surface will create a lower pressure on the downstream side, allowing water to flow more easily in that direction.

4. What are some real-world applications of water flow against an adverse pressure gradient?

Water flow against an adverse pressure gradient is a common occurrence in many natural and man-made systems. Examples include the flow of blood in veins and arteries, the flow of water in rivers and streams, and the flow of fluids in pipes and pumps.

5. How does turbulent flow affect water flow in an adverse pressure gradient?

Turbulent flow, which is characterized by chaotic and irregular motion, can affect water flow in an adverse pressure gradient by disrupting the cohesive and adhesive properties of water molecules. This can result in a slower and less efficient flow, as well as increased energy loss due to friction and turbulence.

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