Learning Forum

[pv00170]

Does Report definition > Force report > Drag > Drag force give the force of static pressures?

 

[Nikhil Narale]

Hello, 

The drag force is calculated by integrating pressure over an object's surface. Bernoulli's principle dictates that pressure and velocity vary along a streamline to preserve total pressure. This results in the dynamic head (velocity) becoming zero at the surface of an obstacle, and hence static pressure becomes dominant. With that said, the drag force also keeps the viscous forces into account in addition to the static pressure distribution. 

[pv00170]

Yes, I understand that if the object's surface is a no-slip boundary, velocity is zero at the surface, and therefore dynamic pressures become zero, leading total pressure be equal to static pressure.

I did an analysis of water pressures in a bridge, and the following image is refeering to the pressures and forces of the upper part of the slab. I obtained the static, dynamic and total pressures of the upper part of the slab, and I can see that dynamic pressures are far from 0. I did the integral of pressures and I got the forces in (N) which can be seen in the left-hand side of the image.

At the same time, values for static, dynamic and total forces are the same as if I use Surface report > Area weighted average > Static pressure, dynamic pressure and total pressure, respectively.

On the right hand side of the image the Report definition > Lift force, gives me the same exact value as the static force computed by myself and by Surface report.

[pv00170]

Dear Nikhil, any update?