Von Karman and Prandtl laws

• foo9008
In summary, the conversation is about finding the friction factor for rough and smooth pipes using the vont karman and prandit laws. The individual is unsure which formula to use and is considering doing both and comparing the results. They have also calculated the friction factor for rough pipe and found it to be 0.017. However, they are unsure how to find the friction factor for smooth pipe using the same laws. They have obtained two different values using a scientific calculator, 0.017 and 0.014, and are asking for input on which value to choose.

Homework Statement

there are 2 formula of vont karman and prandit laws to find the friction factorfor rough pipe and smooth pipe , which formula should i use for this question?

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P/ s : I'm asked to find the friction factor using the vont karman and prandit laws.

The Attempt at a Solution

it didnt stated whether it's smooth or rough pipe , which formula should we use?

I was going to propose you do both (assuming some reasonable ##e## for galvanized ion pipe ) and compare ...

On the other hand, you do have the data to calculate Re so I certainly wouldn't leave out that one...

foo9008
BvU said:
I was going to propose you do both (assuming some reasonable ##e## for galvanized ion pipe ) and compare ...

On the other hand, you do have the data to calculate Re so I certainly wouldn't leave out that one...
well , i have found that the f for rough pipe is 0.017 , nut i am not sure how to find f for smooth pipe using von karman and Prandlt laws ... for smooth pipe , i have 1 / ( surd f ) = 2 log [(3.72 x 10^5) (surd f ) / 2.51 ]

P/ s: by using scientific calculator , i get the f for smooth pipe is 0.014 , which value should i choose ? f= 0.017 or 0.014 ?

Edit : Duplicate information removed .

Last edited:
Nidum said:
Edit : Duplicate information removed .
so , do you have any comment on this question / which is correct ?

What are the Von Karman and Prandtl laws?

The Von Karman and Prandtl laws are two fundamental laws in fluid dynamics that describe the behavior of boundary layers, which are thin layers of fluid that form near a solid surface in a moving fluid.

What is the Von Karman law?

The Von Karman law states that the ratio of the shear stress to the square root of the fluid's density is constant throughout the boundary layer, regardless of the fluid's viscosity. This law is also known as the "law of the wall" because it describes the shear stress near the wall of the boundary layer.

What is the Prandtl law?

The Prandtl law states that the thickness of the boundary layer is proportional to the square root of the distance from the leading edge of the object. This law is also known as the "law of the boundary layer thickness" and is used to predict the thickness of the boundary layer at different points along an object.

How are the Von Karman and Prandtl laws related?

The Von Karman and Prandtl laws are related because they both describe different aspects of boundary layers and are used to analyze the behavior of fluids near a solid surface. The Von Karman law describes the shear stress near the wall of the boundary layer, while the Prandtl law describes the thickness of the boundary layer.

What are the applications of the Von Karman and Prandtl laws?

The Von Karman and Prandtl laws have numerous applications in fluid dynamics, including the design of aerodynamic surfaces for aircraft, the prediction of drag and lift forces, and the analysis of heat and mass transfer in boundary layers. These laws are also used in the development of wind turbines, automobiles, and other vehicles that interact with fluid flow.