SBMDStudent said:I was hoping someone could give me an explanation as to why resistance of a fluid moving through a tube changes from being determined by viscosity in conditions of laminar flow to being determined by density in conditions of turbulent flow.
Thanks in advance.
boneh3ad said:When the flow transitions to turbulence, as mentioned before, there is a lot of mixing involved and this tends to create a more highly curved velocity profile than the laminar case. Since the flow resistance is related to the velocity gradient at the walls, a turbulent flow will have a greater pressure drop than an equivalent laminar boundary layer. Still, it will not only depend on density in general. It will have similar dependencies to the laminar case, though with different relationships between parameters.
It think we are in total agreement. The only thing I was really questioning was the statement the velocity profile in turbulent flow is more curved than in laminar flow. I wanted to clarify that it is actually flatter in the central region of the flow.boneh3ad said:All of which is supported by what I just said, particularly in light of the fact that the wall shear stress that gives rise to pressure drop is dependent on the wall-normal velocity gradient at the wall.
Agreed (again). I was strictly endeavoring to be more precise and avoid confusion for those new to this material.boneh3ad said:It is more sharply curved where it counts, near the wall.
Laminar flow is a type of fluid motion that occurs when a fluid moves in a smooth, orderly manner. In contrast, turbulent flow is a type of fluid motion that occurs when a fluid moves in an irregular, chaotic manner.
Laminar flow is typically caused by low fluid velocity, low fluid viscosity, and/or small pipe diameters. Turbulent flow is typically caused by high fluid velocity, high fluid viscosity, and/or large pipe diameters.
The Reynolds number is used to determine whether flow is laminar or turbulent. If the Reynolds number is less than 2000, the flow is considered laminar. If the Reynolds number is greater than 4000, the flow is considered turbulent. Between 2000 and 4000, the flow may transition between laminar and turbulent.
Laminar flow is characterized by smooth, parallel layers of fluid that do not mix or swirl. Turbulent flow is characterized by mixing and swirling of fluid layers, resulting in high levels of fluid mixing and energy dissipation.
Laminar flow is often desired in applications where a smooth flow is necessary, such as in certain chemical reactions or in the design of aircraft wings. Turbulent flow is often used in applications where mixing and energy dissipation are desired, such as in heat exchangers and in the generation of electricity through wind turbines.