MODELING THE STEADY CAVITATING FLOW IN HYDRAULIC PIPELINES BY MEANS OF A CONSISTENT THERMODYNAMIC THEORY
Alexandre Hastenreiter Assumpção1; Felipe Bastos de Freitas Rachid1; Maria Laura Martins-Costa2; Rogério Martins Saldanha da Gama3
1 UFF; 2 Universidade Federal Fluminense; 3 Universidade do Estado do Rio de Janeiro
doi:10.20906/CPS/COB-2015-2740
Resumo
This work presents a consistent thermodynamic model to describe the cavitating flow in hydraulic pipelines. Although the model is capable to describe the cavitation phenomenon in unsteady as well as steady states, the application presented herein is restricted to slack flow, which take places under steady state. The flow is assumed to be homogeneous and isothermal and the fluid is regarded as a pseudo-mixture, comprising the liquid and the vapor phase along with an inert gas. The constituents are assumed to be compressible and to coexist at every material point and time instant. The balance equations of mass for each constituent are considered in the model, along with one balance equation of momentum for the mixture as a whole within the one-dimensional context. The existence of a small amount of inert gas along with the vapor ensures the necessary thermodynamic condition to describe the opening and closing of the cavity. It also allows the description of the cavitation phenomenon in any region of the fluid flow domain by means of a same set of equations. The phase change transformation is properly accounted for as an irreversible process. The obtained results by means of a simple numerical simulation show that model is capable to coherently describe the continuous growing of the vapor cavity until the flow becomes sonic.
Palavras-chave: inert gas; thermodynamics of irreversible processes; pipelines; vaporous cavitation