you are right, it should be md.add_linear_term(mim9, '(alpha*Grad(p)-g*(rho_tissue-rho_air*Heaviside(X(1))-rho_water*Heaviside(-X(1))))*Test_u(1)' )
BR Kostas On Fri, Nov 19, 2021 at 11:47 PM Lesage,Anne Cecile J < ajles...@mdanderson.org> wrote: > Dear Konstantinos > > > > I understand the use of the Heaviside function but I do not get how you > impose that the gravity is along the x axis > > > > Thank you > > Regards > > AC > > > > > > *From:* Konstantinos Poulios <logar...@googlemail.com> > *Sent:* Wednesday, November 17, 2021 1:37 AM > *To:* Lesage,Anne Cecile J <ajles...@mdanderson.org> > *Cc:* getfem-users@nongnu.org > *Subject:* [EXT] Re: adding buoyancy forces to Biot poroelastic equations > > > > *WARNING: *This email originated from outside of MD Anderson. Please > validate the sender's email address before clicking on links or attachments > as they may not be safe. > > > > Dear Anne-Cecile, > > > > The GetFEM model object does not differentiate between left and right side > of an equation (there is no reason for splitting equations like this), all > equations are assumed to be in the form R(...)=0. So just move all terms on > the same side. > > > > The equation you provide is in strong form, you need to convert it to the > respective weak form and apply the necessary integration by parts to get > rid of higher order derivatives as you showed in your add_linear_term > expression. After all these steps you should have > > > > md.add_linear_term(mim9, > 'G*Grad(u):Grad(Test_u)+G/(1-2*nu)*Div(u)*Div(Test_u)+(alpha*Grad(p)-g*(rho_tissue-rho_air*Heaviside(X(1))-rho_water*Heaviside(-X(1)))).Test_u' > ) > > > > you can also choose to split the term in two lines > > > > md.add_linear_term(mim9, > 'G*Grad(u):Grad(Test_u)+G/(1-2*nu)*Div(u)*Div(Test_u)') > > md.add_linear_term(mim9, > '(alpha*Grad(p)-g*(rho_tissue-rho_air*Heaviside(X(1))-rho_water*Heaviside(-X(1)))).Test_u' > ) > > > > but there is no reason for not keeping everything just in one term. > > > > > > BR > > Kostas > > > > > > On Tue, Nov 16, 2021 at 11:12 PM Lesage,Anne Cecile J < > ajles...@mdanderson.org> wrote: > > Dear all > > > > To implement the building of my fem matrix for the mechanical equilibrium, > I presently write > > md.add_linear_term(mim9, > 'G*Grad(u):Grad(Test_u)+G/(1-2*nu)*Div(u)*Div(Test_u)+alpha*Grad(p).Test_u' > ) > > > > How can i add an additional buoyancy terms to the equation (see right-hand > side attached equation picture)? > > gravity is vector g = - 9180 N along the x axis for my mesh > > rhot (density tissue is constant) but rhof = rho water for x<0 and rhof = > rho air for x>0 > > > > Thank you > > Anne-Cecile Lesage > > > > > > > > The information contained in this e-mail message may be privileged, > confidential, and/or protected from disclosure. This e-mail message may > contain protected health information (PHI); dissemination of PHI should > comply with applicable federal and state laws. If you are not the intended > recipient, or an authorized representative of the intended recipient, any > further review, disclosure, use, dissemination, distribution, or copying of > this message or any attachment (or the information contained therein) is > strictly prohibited. If you think that you have received this e-mail > message in error, please notify the sender by return e-mail and delete all > references to it and its contents from your systems. > > The information contained in this e-mail message may be privileged, > confidential, and/or protected from disclosure. This e-mail message may > contain protected health information (PHI); dissemination of PHI should > comply with applicable federal and state laws. If you are not the intended > recipient, or an authorized representative of the intended recipient, any > further review, disclosure, use, dissemination, distribution, or copying of > this message or any attachment (or the information contained therein) is > strictly prohibited. If you think that you have received this e-mail > message in error, please notify the sender by return e-mail and delete all > references to it and its contents from your systems. >
