18 Replies Latest reply on Apr 30, 2014 2:48 AM by Jared Conway

    Erosion Rate using CFD

    Alain Agius

      Hi there I am a final year mechanical engineering student currently working on my thesis. The study is on the erosion rate of an abrasive particle air jet (like a water jet cutter but with air) The model is in an attachment. the sides are lids at atm. pressure and the inlet pressure is at 8 Bar, the nozzle walls are real walls. I manage to simulate the air flow and include a particle study, however I have a bit of a problem.

      When I include the particle study to see the erosion on the plate which is beneath the nozzle, I include a wall condition, however it seems that the only property of the material it considers is the density of the material, is there a way in which it can differentiate say if it were glass or aluminium for example?

       

      Thanks

      Al

        • Re: Erosion Rate using CFD
          Jared Conway

          what are you trying to learn from the erosion study?

          if you take a look at the equation, the parameters that you define are not directly related to the material but rather the interaction between the material and the erosion medium. if you have those parameters for the 2 cases you should be able to see a difference between them.

          but if you're expecting to just plug in a value for glass and one for aluminum and see the difference, unfortunately that isn't possible yet. consider the material properties you enter for the materials, it doesn't include the erosion parameters.

            • Re: Erosion Rate using CFD
              Alain Agius

              Hi Jared thank you for the quick reply, yes to be honest I thought that maybe by applying the materials in the assembly it would make a difference since the material properties would be applied to the part, no matter.

              Another question then, when inserting wall conditions there are a few parameters such as Erosion Coefficient, Function of Particle Diameter, Function of Impact Angle and Function of relative particle velocity, unfortunately I can't understand how to use these, could you offer any advice?

               

              Thanks again

              • Re: Erosion Rate using CFD
                Alain Agius

                I'm asking because whenever I try search for anything related to erosion coefficient I come up blank and can't find any content regarding wall parameters in Solidworks

                  • Re: Erosion Rate using CFD
                    Jared Conway

                    have you checked the solidworks KB? i believe the last time i spoke to the developers about this they posted an article or reference for where the method came from. however regarding the actual constants, i do not believe that they are easy to come by and that unless you have done the experimentation to get the constants, you'll have to use the same constants between your 2 geometries/conditions and compare the relative changes in erosion.

                • Re: Erosion Rate using CFD
                  John Staudt

                  PMFBI, but I am dealing with the same issues of the meaning of the parameters for reflection and wall properties.  I have a working model, thanks to all the help from technical support, but my results for erosion rates are off by orders of magnitude, most likely due to not knowing what values to use as program input for K, C, f, and b.

                   

                  The article in the KB references the technical reference that comes with the program, and the section "Two-phase (fluid + particle) Flows".  There it shows the formula used for erosion mass rate.  However the variable names do not match between the program input and the formula.  The KB article says that C is equal to the term f2(dpi) and f is equal to the term fli(alpha pi).  b is the same as the eponent b in the formula and K is the same as K.  It gives no indication of what they mean or how to find them.

                   

                  C and f are described as "user-specified dimensionless functions" and K is "the impingement erosion coefficient specified by the user".

                   

                  There is no reference given in this section and I don't see a reference in the reference section that speaks to erosion specifically.  Can someone explain in more detail what these variables represent and how to go about finding them experimentally? 

                    • Re: Erosion Rate using CFD
                      Jared Conway

                      is this for a commercial project or educational project? IE, do you have access to a reseller technical support provider? they may be able to get you more info from the developers on this.

                       

                      second, do you have the ability to perform the experiment or are you hoping to find the information online? my last experience with this was that those that are needing to use this equation, already have the information and it is not generally available. and generally they are privy to the equation and what the parameters mean. but that is moot if you don't have the ability to do the experiment or don't already have the parameters. which is where i was stuck last time with my customer.

                        • Re: Erosion Rate using CFD
                          John Staudt

                          Thanks for the quick reply.

                           

                          It is commercial and I have been working with both my reseller technical support and SW support, and no, I don't have the ability to do the required experimental work.  The problem is that the folks that do the work and have the answers don't like to share.  It is an energy production related project and the big guys don't play well with others. 

                           

                          I have worked in the industry for over 40 years whith lots of design experience and 10+ years of FEA, but this is my first venture into flow studies and CFD.

                           

                          I do have some emperical data, so I have a feel for what the answer needs to be, but I would love to have a better understanding of the parameters rather than fudge numbers into the program until I get something that looks reasonable.  That works for a given set of conditions, but doesn't help when the conditions change.

                           

                          Any insights, references, resources would be greatly appreciated.

                      • Re: Erosion Rate using CFD
                        Alain Agius

                        Hi Jared, if you do manage to get your hands on any erosion info would you be kind enough to share it? The thing is considering this is for my thesis I would have to explain what the model is doing to generate the erosion rate (how it is being calculated) and I can't seem to find any material on it