Innitial Nozzles Analysis CFD – ongoing

Hi, this is initial analysis of a nozzle working under pressure, fluid used in the analysis is water. Used software is LISA FEA 8.0.0.

1st stage:

CFD nozzles converged result

Conditions:

Inlet pressure 200bar

Outlet pressure 1bar

4 different geometries for Laval nozzle and 2 variations for Shesterenko nozzle.

This initial analysis was to obtain direction of the design geometry changes to achieve high velocities. Although first results are strongly affected by computational error assumed but give very good insight how the velocities field is changing.

Error is due to:

  • coarse mesh
  • lack of convergence
  • software doesn’t include compressibility of a fluid (velocities are expected to be >1Mach)

Despite the error it is clear that Shesterenko and Lavala nozzles design requirement depend on the inlet and outlet angle, size of the narrowing, shapes of the edges in the narrowing area, inlet and outlet pressure, internal wall roughness (surface finish). From computational point of view the type of used element, size of used element, boundary conditions, solvers capabilities to deal with natural (turbulent and compressible flow).

This is just a begin of the analysis and so far output data shouldn’t be considered as results but just as guidance.

As the software used has got limitations with dealing with compressible and turbulent flow then next analysis will be probably done using ELMER or OpenFoam, OpenFOAM is using proper CFD approach which is Final Volume Method.

Results in the output scale are:

  • velocity m/s
  • pressure Pa
  • vorticity s^-1

2nd Stage analysis:

Analysis using LISA, Szesterenko version 4 was used as the highest velocities were present. This time after changing scale to mm, adjusting mesh, changing convergence to 0.01 with the relaxation factor 0.01, Navier-Stokes equation was used so turbulent flow was taken under consideration. Unfortunately this is the most we can get out of LISA and results including flow compression and in cavity phenomena phase transition which will be present, probably will require strong CFD code such as ELMER or OpenFOAM.

 

Results (please use Open Office):

  1. Results photo gallery of few type of nozzles but with very high error.
  2. Results photo gallery obtained by adjusting settings and input information, results converged which means that less than 1% error is present. It applies just to the simplification in LISA of complicated phenomena, hopefully other packages will help obtaining expected results.
  1. CFD nozzles initial results non converged LISA
  2. CFD shesterenko nozzle converged LISA