Verification and validation of large eddy simulation with Nek5000 for cold leg mixing benchmark

Jonathan K. Lai, Elia Merzari, Yassin A. Hassan, Paul Fischer, Oana Marin

Research output: Contribution to journalArticle

Abstract

Large eddy simulation (LES) of an experimental benchmark investigating buoyant mixing among two fluids is developed for verification and validation. Flow physics involve a completely closed system where after a valve is opened, two initially stationary fluids with different densities are allowed to mix. The Boussinesq approximation and low-Mach equations are coded into spectral element code Nek5000 to predict the buoyancy forces, and miscibility is accounted for using the advection-diffusion equation for concentration. Due to computational costs of higher order solutions, current analysis consists of initial flow development after the valve is opened. Minor differences between the models and Schmidt number are found within the turbulent spectrum and time integrated quantities. Moreover, solutions for higher polynomial orders are compared to quantify error due to spatial discretization. Error estimates using a posteriori spectral derivation of truncation and quadrature error are also calculated. Validation with particle image velocimetry (PIV) reveals good prediction of both average and fluctuating components of the primary flow within the cold leg but less accurate results in the downcomer. It is concluded that instabilities due to resolving more of the interface using the high molecular Schmidt number is essential for accurately predicting this type of flow.

Original languageEnglish (US)
Article number110427
JournalNuclear Engineering and Design
Volume358
DOIs
StatePublished - Mar 2020

Fingerprint

large eddy simulation
Large eddy simulation
Schmidt number
Fluids
Advection
Buoyancy
advection-diffusion equation
Boussinesq approximation
truncation errors
Velocity measurement
Mach number
fluid
fluids
particle image velocimetry
Physics
Solubility
advection
buoyancy
quadratures
Polynomials

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Materials Science(all)
  • Safety, Risk, Reliability and Quality
  • Waste Management and Disposal
  • Mechanical Engineering

Cite this

Lai, Jonathan K. ; Merzari, Elia ; Hassan, Yassin A. ; Fischer, Paul ; Marin, Oana. / Verification and validation of large eddy simulation with Nek5000 for cold leg mixing benchmark. In: Nuclear Engineering and Design. 2020 ; Vol. 358.
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Verification and validation of large eddy simulation with Nek5000 for cold leg mixing benchmark. / Lai, Jonathan K.; Merzari, Elia; Hassan, Yassin A.; Fischer, Paul; Marin, Oana.

In: Nuclear Engineering and Design, Vol. 358, 110427, 03.2020.

Research output: Contribution to journalArticle

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