Effects of variable air properties on transient natural convection for large temperature differences

Armengol, Jan Mateu; Bannwart, Flávio; Xamán, J.; Santos, Rogério Gonçalves dos

doi:10.1016/j.ijthermalsci.2017.05.024

Cited by 17 publications

(6 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After a steep drop during the initial stages of the simulation, the Nusselt number increases gradually to a steady state value. Our solution is in good agreement with the reference solution of [72], with the steady state solutions differing by 1.3%. Noting that the solution methodology followed in the reference study is based on the low-Mach number asymptotic expansion of the Navier-Stokes equations, and therefore is significantly different to the present method, the agreement between the two solutions is considered satisfactory.…”

Section: Thermally Driven Flow In a Differentially Heated Cavitysupporting

confidence: 79%

“…For temperature differences less than approximately 30 K the flow of air is considered incompressible [67], and the Oberbeck-Boussinesq approximation is typically adopted [68,69,70]. Outside the limits of the Oberbeck-Boussinesq approximation, weak compressibility effects appear, 16 and different low-Mach methodologies were utilised to study these effects [71,72,73]. For the purposes of this study, this test case helps to assess the ability of the methodology to accurately incorporate the effects of viscosity and thermal conductivity.…”

Section: Thermally Driven Flow In a Differentially Heated Cavitymentioning

confidence: 99%

“…The case simulated here follows the setup presented in [71,72] and involves a temperature difference ∆T = 720 K, around a reference temperature of T r = 600 K. The reference thermophysical quantities and the height of the cavity L are chosen such that the Rayleigh and Prandtl numbers are equal to, Ra = gρ 2 r κ p β∆T L 3 µλ = 10 6 , and Pr =…”

Section: Thermally Driven Flow In a Differentially Heated Cavitymentioning

confidence: 99%

See 2 more Smart Citations

A pressure-based diffuse interface method for low-Mach multiphase flows with mass transfer

Demou,

Scapin,

Pelanti

et al. 2021

Preprint

View full text Add to dashboard Cite

This study presents a novel pressure-based methodology for the efficient numerical solution of a four-equation two-phase diffuse interface model. The proposed methodology has the potential to simulate low-Mach flows with mass transfer. In contrast to the classical conservative four-equation model formulation, the adopted set of equations features volume fraction, temperature, velocity and pressure as the primary variables. The model includes the effects of viscosity, surface tension, thermal conductivity and gravity, and has the ability to incorporate complex equations of state. Additionally, a Gibbs free energy relaxation procedure is used to model mass transfer. A key characteristic of the proposed methodology is the use of high performance and scalable solvers for the solution of the Helmholtz equation for the pressure, which drastically reduces the computational cost compared to analogous density-based approaches. We demonstrate the capabilities of the methodology to simulate flows with large density and viscosity ratios through extended verification against a range of different test cases. Finally, the potential of the methodology to tackle challenging phase change flows is demonstrated with the simulation of three-dimensional nucleate boiling.

show abstract

Section: Thermally Driven Flow In a Differentially Heated Cavitysupporting

confidence: 79%

Section: Thermally Driven Flow In a Differentially Heated Cavitymentioning

confidence: 99%

Section: Thermally Driven Flow In a Differentially Heated Cavitymentioning

confidence: 99%

See 1 more Smart Citation

A pressure-based diffuse interface method for low-Mach multiphase flows with mass transfer

Demou,

Scapin,

Pelanti

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Typically, the height of the cavity is taken as the reference length (l r = L z ), while the reference velocity and time are defined as u r = α/l r and t r = l 2 r /α. The case simulated here follows the setup presented in several studies [61,62,60] with Ra= 10 6 and Pr= 0.71. The domain boundaries are solid walls, and no-slip boundary conditions are applied.…”

Section: Differentially Heated Cavitymentioning

confidence: 99%

FluTAS: A GPU-accelerated finite difference code for multiphase flows

Crialesi-Esposito¹,

Scapin²,

Demou³

et al. 2022

Preprint

View full text Add to dashboard Cite

We present the Fluid Transport Accelerated Solver, FluTAS, a scalable GPU code for multiphase flows with thermal effects. The code solves the incompressible Navier-Stokes equation for two-fluid systems, with a direct FFTbased Poisson solver for the pressure equation. The interface between the two fluids is represented with the Volume of Fluid (VoF) method, which is mass conserving and well suited for complex flows thanks to its capacity of handling topological changes. The energy equation is explicitly solved and coupled with the momentum equation through the Boussinesq approximation. The code is conceived in a modular fashion so that different numerical methods can be used independently, the existing routines can be modified, and new ones can be included in a straightforward and sustainable manner. FluTAS is written in modern Fortran and parallelized using hybrid * M.C-E. and N.S. contributed equally to this work.

show abstract

“…The second segment is a local pressure (known as the hydrodynamic pressure) that acts just in the momentum equations. Armengol et al 10 and Wan et al 11 employed this algorithm for free convection phenomena with large temperature differences beyond the validity of the OB approximation.…”

Section: Introductionmentioning

confidence: 99%

An efficient and simplified Gay‐Lussac approach in secondary variables form for the non‐Boussinesq simulation of free convection problems

Mayeli

Sheard

2021

Numerical Methods in Fluids

View full text Add to dashboard Cite

The Gay-Lussac (GL) approach is an incompressible-based strategy for non-Boussinesq treatment of the governing equations for free convection problems that is established based on extending the density variations beyond the gravity term. Such a strategy leads to emerging the GL parameter as a non-Boussinesq prefactor of different terms in the governing equations. In this article, the GL approach is expressed/discussed in terms of the secondary variables, that is, vorticity and stream-function, for the first time and a simplified version of this approach is proposed by removing density variations from the continuity equation. The difference of results under the simplified and traditional GL approach ranges within a maximum of 1% for different parameters. The lower computational cost of numerical solution of governing equations in the secondary variables formula and the corresponding convergence rate is scrutinized for the simplified GL approach showing around 25% lower computational cost. The performance of this approach is evaluated at high relative temperature differences against the low Mach number scheme and the Boussinesq approximations. In this respect, natural convection in an annulus cavity is numerically simulated using a CVFEM solver under the aforementioned approximations up to Rayleigh number Ra = 10 5 at Prandtl number Pr = 1 and high relative temperature differences ( = 0.15 and 0.3).The largest deviations found for either the simplified GL or Boussinesq methods from the low Mach number scheme solution are less than 20% for velocity magnitude, 14% for stream function, 6% for vorticity, and 5% for temperature. Results under the three approximations are also analyzed in terms of the skin friction and local and average Nusselt number, indicating that the Gay-Lussac approach requires some revisions to act more accurately than the classical Boussinesq approximation at high relative temperature differences in natural convection problems, especially within the convection dominated regime.

show abstract

Effects of variable air properties on transient natural convection for large temperature differences

Cited by 17 publications

References 41 publications

A pressure-based diffuse interface method for low-Mach multiphase flows with mass transfer

A pressure-based diffuse interface method for low-Mach multiphase flows with mass transfer

FluTAS: A GPU-accelerated finite difference code for multiphase flows

An efficient and simplified Gay‐Lussac approach in secondary variables form for the non‐Boussinesq simulation of free convection problems

Contact Info

Product

Resources

About