{"id":163436,"date":"2021-10-27T09:38:14","date_gmt":"2021-10-27T09:38:14","guid":{"rendered":"\/forum\/forums\/topic\/conservation-of-momentum-for-two-phase-turbulent-flow-using-rans\/"},"modified":"2021-11-18T07:32:22","modified_gmt":"2021-11-18T07:32:22","slug":"conservation-of-momentum-for-two-phase-turbulent-flow-using-rans","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/conservation-of-momentum-for-two-phase-turbulent-flow-using-rans\/","title":{"rendered":"Conservation of Momentum for two-phase turbulent flow using RANS."},"content":{"rendered":"
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Good Morning, <\/p>\n

I have a two rather theoretical questions concerning the equations solved using the Multiphase Eulerian model in Fluent.<\/p>\n

Ansys Fluent Theory Guide gives us equation 14-181 (section 14.5.4.2.2.<\/a>) <\/p>\n

When using a turbulence model such as the k – ω SST model, the momentum equation becomes a time averaged of the original equation in which quantities (velocities, pressure) are decomposed into a time – averaged component and a fluctuation component. The result of such a treatment for a single phase is given in Equation 4.4 (section 4.1.1<\/a>). For a two-phase flow, however, another quantity is introduced, which is the mass transferred from one fluid to the other (in kg\/s). I would assume that this quantity is also decomposed into its time-averaged component and fluctuation component. Therefore, if we denote the time averaged components using an upper-case letter and the fluctuations components using italics, the term <\/p>\n

m_pq*v_pq<\/strong> should become (M_pq+m_pq<\/em>)(V_pq<\/strong>+v_pq<\/em><\/strong>) which yields, after taking the time averaged, to: <\/p>\n

M_pq*V_pq + <\/strong>time_average(m_pq<\/em>*v_pq<\/em><\/strong>)<\/p>\n

(the same applies to m_qp*v_qp<\/strong>) <\/p>\n

As m_pq<\/em> and v_pq<\/em><\/strong> are unknown, how does Fluent solve this ? Or is the term m_pq not decomposed at all? <\/p>\n

My second question concerns the phase stress-strain tensor described in equation 14-177 (Section 14.5.4.1.2<\/a>) Indeed, the tensor uses the bulk viscosity which is only defined in the theory guide for solids. In case of fluids, am I right to assume that the Stokes' hypothesis is taken and therefore, the bulk viscosity λ_q is 0? (Although I guess this should not matter on my current case as it is an incompressible flow and the divergence of the velocity should give 0 so the term with the bulk viscosity should become 0 as well but I would like to understand anyway.)<\/p>\n

Thank you very much for your time and answers .<\/p>\n","protected":false},"template":"","class_list":["post-163436","topic","type-topic","status-closed","hentry","topic-tag-bulk-viscosity-1","topic-tag-conservation-of-momentum","topic-tag-fluent","topic-tag-multiphase","topic-tag-rans"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":[""],"_bbp_old_reply_author_name_id":["Anonymous"],"_bbp_old_is_reply_anonymous_id":["false"],"_btv_view_count":["453"],"_bbp_likes_count":["0"],"_bbp_subscription":["253319"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["163436"],"_bbp_forum_id":["27792"],"_bbp_engagement":["5120","179207"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["195960"],"_bbp_last_active_id":["195960"],"_bbp_last_active_time":["2021-11-18 07:32:22"]},"test":"kefon"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/163436","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/163436\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=163436"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}