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VERSION:2.0
PRODID:-//Memento EPFL//
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SUMMARY:Analysis of head losses in a bulb turbine draft tube by means of u
 nsteady numerical simulations
DTSTART:20170330T140000
DTEND:20170330T150000
DTSTAMP:20260916T084336Z
UID:41ad1671913c5b9582ef8207a20c7b589f884308b21179b693fae349
CATEGORIES:Conferences - Seminars
DESCRIPTION:Sylvia Wilhelm\, Grenoble Institute of Technology/ Ense3\, Lab
 oratoire LEGI\nThe draft tube of a hydraulic turbine is the turbine elemen
 t located downstream of the runner. It has a divergent shape in order to c
 onvert the residual kinetic energy leaving the runner into pressure and th
 us increase the specific energy transfer to the runner. The performances o
 f low head bulb turbines are highly influenced by the head losses in the d
 raft tube. The prediction of these head losses in a design process is ther
 eby a major issue. The numerical prediction of the head losses in the draf
 t tube is a real challenge because the flow in the draft tube is highly un
 steady with high Reynolds numbers\, a swirl and an adverse pressure gradie
 nt.\n\nThese characteristics render conventional industrial approaches not
  appropriate for head losses prediction. The objective of this work is two
 fold:\n\n(i) to improve the numerical prediction of the turbulent flow in 
 the draft tube by using URANS and LES unsteady approaches and paying speci
 al attention to the description of the inlet boundary conditions of the dr
 aft tube and\n(ii) to conduct a detailed analysis of the energy transfers 
 in the draft tube in order to better understand the origin of the head los
 ses.\n\nAn unsteady inlet boundary condition for the simulations reproduci
 ng the flow field at the runner outlet is developed. Numerical results are
  compared to experimental measurements in order to evaluate the predictive
  capacity of each turbulence modelling approach (URANS and LES). This vali
 dation step highlights the importance of defining properly the three veloc
 ity components at the draft tube inlet. Thanks to a detailed analysis of t
 he mean kinetic energy balance in the draft tube\, the hydrodynamic phenom
 ena responsible for head losses are identified. The head losses prediction
  differences between URANS and LES are thus analyzed in detail and possibl
 e improvements for the head losses prediction are identified. Finally\, th
 is analysis enables to understand the head losses evolution observed betwe
 en several operating points of the turbine.
LOCATION:ME B1 B10 https://plan.epfl.ch/theme/generalite_thm_v2?lang=en&ro
 om=me%20b1%2010&dim_floor=1&dim_lang=en&tree_groups=centres_nevralgiques%2
 Cacces%2Cmobilite_reduite%2Censeignement%2Ccommerces_et_services%2Cvehi
STATUS:CONFIRMED
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