Hi, everybody! In simulating the flow of a circular cylinder, some papers give the value of the base pressure coefficients. I donnot know why they give the parameter. In other words, what is the main role of the base pressure in simulating the flow of circular cylinder? For example, how does it relate to drag coefficient? Thanks in advance!

For incompressible flow it doesn't matter. Is this what you are simulating: incompressible vortex-shedding over a circular cylinder? Or is it compressible flow?

for low speed flows, setting a base pressure reduces rounding errors. it's not critical, but helpful. 101325 Pa would be OK for base pressure.

I'm wondering if the original poster is referring to the pressure in the separated base region of the cylinder.

Are you sure that the paper talks about a cylinder in cross-flow? The term base-pressure is used for the pressure in the separated region of a cylinder in flow direction (launch vehicle, missile, ...)

Sorry very much for all! It is my wrong that I am obscure in posting my question. In fact, base pressure means the pressure of base point just behind circular cylinder. Waiting for answer!

I still think it should be "initialized" to 101325 Pa, even if the steady/quasi-steady/unsteady solution develops to a partial vacuum downstream of the cyl.

In incompressible flow the absolute pressure is irrelevant. However, you can use this parameter to compare your solution with the experiments. Given a certain mean flow, the "base pressure" depends on the average points of separation on the cylinder. So the base pressure might be used as one (of many) measures to verify that you get your solution right, at least in a very general and average sense. I am sure the "base pressure coefficient", you mentioned is nondimensionalized with mean flow variables, although you didn't specify the formula. In that case, the absolute pressures of your mean flow and base point are really not important for validation purposes, as long as you get the correct coefficient. Do you?