Hypermesh CFD Forces calculation in Engineering Quantities

Victor_op

Hello everyone.

I am currently performing CFD simulations on a reentry capsule. I am having problems in understanding how the Engineering Quantities - Forces work.

What are the units of the force?

Does the slice plane I use affect on the force´s value?

I am working in milimetres in the sketch and mesh ribbons, and I am sure my preferences are set in N mm kg s. I am asking these questions because the results are not physically coherent since I should be getting much much much lower values of force.

I am also sure that my mesh is correctly refined and the geometry does not have any error.

Can someone help me with these doubts?

Thank you all.

acupro

At the solver level, there is no concept of units. All values (including the nodal positions - thus model dimensions) need to represent a consistent set of units. For example if the material properties have values consistent with MKS, then everything must be represented in MKS. One check - in the .Log file just before the domain decomposition process the min/max locations in each direction are presented, as well as the overall bounding box. Are those values what you expect? Next check the input file for values in material properties, boundary conditions, etc. Are those values consistent with the units system represented by the bounding box sizes?

In other words, if the material properties represent MKS - like air density 1.225 kg/m3 - but the bounding box sizes/values are consistent with sizes in mm - there is a units consistency problem.