Abstract
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Supervisors/Advisors 

Award date  1 Mar 2002 
Place of Publication  Espoo 
Publisher  
Print ISBNs  951385969X 
Electronic ISBNs  9513859703 
Publication status  Published  2002 
MoE publication type  G5 Doctoral dissertation (article) 
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Keywords
 multiphase flow
 multifluid modelling
 interphase coupling
 phasic pressures
 numerical methods
 Control Volume Method
 Body Fitted Coordinates
 fluidized beds
 chemical reactors
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Numerical treatment of interphase coupling and phasic pressures in multifluid modelling : Dissertation. / Karema, Hannu.
Espoo : VTT Technical Research Centre of Finland, 2002. 78 p.Research output: Thesis › Dissertation › Collection of Articles
TY  THES
T1  Numerical treatment of interphase coupling and phasic pressures in multifluid modelling
T2  Dissertation
AU  Karema, Hannu
PY  2002
Y1  2002
N2  This thesis work concentrates on the area of dispersed multiphase flows and, especially, to the problems encountered while solving their governing equations numerically with a collocated Control Volume Method (CVM). To allow flexible description of geometry all treatment is expressed in a form suitable for local Body Fitted Coordinates (BFC) in a multiblock structure. All work is related to conditions found in a simplified fluidized bed reactor. The problems covered are the treatment and efficiency of interphase coupling terms in sequential solution, the exceeding of the bounds of validity of the shared pressure concept in cases of high dispersed phase pressure and the conservation of mass in momentum interpolation for rapidly changing source terms. The efficiency of different interphase coupling algorithms is studied in typical fluidized bed conditions, where the coupling of momentum equations is moderate in most sections of the bed and where several alternatives of different complexity exist. The interphase coupling algorithms studied are the partially implicit treatment, the Partial Elimination Algorithm (PEA) and the SImultaneous solution of Nonlinearly Coupled Equations (SINCE). In addition to these special treatments of linearized coupling terms, the fundamental ideas of the SINCE are applied also to the SIMPLE(C) type pressure correction equation in the framework of the Inter Phase Slip Algorithm (IPSA). The resulting solution algorithm referred to as the InterPhase Slip Algorithm  Coupled (IPSAC) then incorporates interface couplings also into the mass balancing shared pressure correction step of the solution. It is shown that these advanced methods to treat interphase coupling terms result in a faster convergence of momentum equations despite of the increased number of computational operations required by the algorithms. When solving the entire equation set, however, this improved solution efficiency is mostly lost due to the poorly performing pressure correction step in which volume fractions are assumed constant and the global mass balancing is based on shared pressure. Improved pressure correction algorithms utilizing separate fluid and dispersed phase pressures, the Fluid Pressure in Source term (FPS) and the Equivalent Approximation of Pressures (EAP), are then introduced. Further, an expanded RhieChow momentum interpolation scheme is derived which allows equal treatment for all pressures. All the computations are carried out in the context of a collocated multiblock control volume solver CFDSFLOW3D.
AB  This thesis work concentrates on the area of dispersed multiphase flows and, especially, to the problems encountered while solving their governing equations numerically with a collocated Control Volume Method (CVM). To allow flexible description of geometry all treatment is expressed in a form suitable for local Body Fitted Coordinates (BFC) in a multiblock structure. All work is related to conditions found in a simplified fluidized bed reactor. The problems covered are the treatment and efficiency of interphase coupling terms in sequential solution, the exceeding of the bounds of validity of the shared pressure concept in cases of high dispersed phase pressure and the conservation of mass in momentum interpolation for rapidly changing source terms. The efficiency of different interphase coupling algorithms is studied in typical fluidized bed conditions, where the coupling of momentum equations is moderate in most sections of the bed and where several alternatives of different complexity exist. The interphase coupling algorithms studied are the partially implicit treatment, the Partial Elimination Algorithm (PEA) and the SImultaneous solution of Nonlinearly Coupled Equations (SINCE). In addition to these special treatments of linearized coupling terms, the fundamental ideas of the SINCE are applied also to the SIMPLE(C) type pressure correction equation in the framework of the Inter Phase Slip Algorithm (IPSA). The resulting solution algorithm referred to as the InterPhase Slip Algorithm  Coupled (IPSAC) then incorporates interface couplings also into the mass balancing shared pressure correction step of the solution. It is shown that these advanced methods to treat interphase coupling terms result in a faster convergence of momentum equations despite of the increased number of computational operations required by the algorithms. When solving the entire equation set, however, this improved solution efficiency is mostly lost due to the poorly performing pressure correction step in which volume fractions are assumed constant and the global mass balancing is based on shared pressure. Improved pressure correction algorithms utilizing separate fluid and dispersed phase pressures, the Fluid Pressure in Source term (FPS) and the Equivalent Approximation of Pressures (EAP), are then introduced. Further, an expanded RhieChow momentum interpolation scheme is derived which allows equal treatment for all pressures. All the computations are carried out in the context of a collocated multiblock control volume solver CFDSFLOW3D.
KW  multiphase flow
KW  multifluid modelling
KW  interphase coupling
KW  phasic pressures
KW  numerical methods
KW  Control Volume Method
KW  Body Fitted Coordinates
KW  fluidized beds
KW  chemical reactors
M3  Dissertation
SN  951385969X
T3  VTT Publications
PB  VTT Technical Research Centre of Finland
CY  Espoo
ER 