Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session J17: Free and Forced Convection |
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Chair: Jinzi Huang, NYU Shanghai Room: 145B |
Sunday, November 19, 2023 4:35PM - 4:48PM |
J17.00001: An experimental study on the onset of centrifugal effects in turbulent rotating thermal convection Yun-Bing Hu, Lin Sun, Ke-Qing Xia Due to its relevance to the geo- and astrophysical flows, geostrophic turbulence, involving strong Coriolis effect and intensive turbulence, is of interests in the studies of turbulent rotating Rayleigh-Bénard convection (RRBC). However, the effect of the unavoidable centrifugal force on the geostrophic turbulence is often overlooked. Even the basic issue concerning when the centrifugal effect starts to manifest itself is still unresolved. In this talk we present an experimental study of the onset of centrifugal effect (characterized by the onset Froude number Fr_{c}) in RRBC. The onset Froude number Fr_{c} was first inferred from the increased bulk temperatures measured at cell center, which was found to scale with the Rayleigh number as Fr_{c }~ Ra^{0.55}. This behavior can be understood qualitatively by a local force balance argument, which gives out Fr_{c }~ l_{0}/H and thus predicts that l_{0}/H ~ Ra^{0.55}. Here, l_{0} is the mean free distance of the columnar vortices in RRBC. However, the directly measured PIV results of l_{0} does not support this 0.55 scaling. We thereby revised the local force balance argument by introducing a correction term, and the measured results agreed well with the revised argument. These results should be useful for future theoretical studies on the centrifugal effect in RRBC. |
Sunday, November 19, 2023 4:48PM - 5:01PM |
J17.00002: Rayleigh-Bénard thermal convection perturbed by a horizontal heat flux Jinzi M Huang, Jun Zhang Controlling Rayleigh-Bénard convection is important in many scientific and practical applications. In this talk, we present a simple means to control the vertical heat transfer in Rayleigh-Bénard convection by injecting heat through one lateral side of the fluid domain and extracting the same amount of heat from the opposite side. This horizontal heat flux regulates the large-scale circulation, and increases the heat transfer rate in the vertical direction. Our numerical and theoretical studies demonstrate how a classical Rayleigh-Bénard convection responds to such a perturbation, when the system is near or well above the onset of convection. |
Sunday, November 19, 2023 5:01PM - 5:14PM |
J17.00003: Stability of convection with horizontal buoyancy gradients Stefan G Llewellyn Smith, Clément Audefroy, Michael Le Bars Horizontal convection, in which variations in buoyancy exist on horizontal boundaries, are often contrasted to Rayleigh-Bénard convection as having no steady states. In fact there exist exact solutions to the equations of motion with constant horizontal buoyancy gradients and induced flows. The study of these flows goes back to Hart and Weber in the 1970s. We revisit this situation, with a focus on geophysically-relevant boundary conditions. Unlike the case of Rayleigh-Bénard and Orr-Sommerfeld stability, the marginal modes are no longer two-dimensional with zero frequency. We explore the stabilty boundary given by horizontal Rayleigh number in terms of vertical Rayleigh number. Fully three-dimensional modes are investigated. Finallly the energy stability problem is examined. |
Sunday, November 19, 2023 5:14PM - 5:27PM |
J17.00004: Critical modes of convection induced by Joule heating in a liquid metal battery Innocent Mutabazi, Anupam M Hiremath, Harunori N Yoshikawa Liquid metal batteries (LMB) consists of three super-imposed liquids in stable stratificationof density where two liquid metals (electrodes) sandwich a molten salt that serves as an electrolyte [1]. An electric current of density J_{0} is applied through the liquid system. As the electrical conductivity of the electrolyte is much lower than the electrical conductivities of liquid metals, the electric current induces an internal Joule heating with the density q through the electrolyte. In conduction regime, the temperature profile is linear in both the liquid metals and it has a parabolic profile in the electrolyte. The upper part of the electrolyte and the upper electrode are thermally unstable while the lower part of the electrolyte and the lower electrode are thermally stable. |
Sunday, November 19, 2023 5:27PM - 5:40PM |
J17.00005: Melting dynamics of an ice surface in a turbulent shear flow Sofía Angriman, Rui Yang, Christopher J Howland, Roberto Verzicco, Detlef Lohse, Sander Huisman We study the dynamics and morphology of a solid as it melts in an idealized setup: we consider an initially flat solid surface between a heated and a cooled plate, with an imposed mean flow. By means of direct numerical simulations, and using the phase-field method, the equations of motion of the fluid phase are coupled with the heat equation within the solid, and a mean flow is sustained by imposing a fixed pressure gradient in the direction parallel to the plates, for Rayleigh numbers in the range 10ˆ5-10ˆ8 and friction Reynolds numbers in the range 10ˆ2-10ˆ3. We study the formation and evolution of patterns and surface roughness, the melt rate, and the heat exchange between the solid and liquid phases while systematically varying the intensity of the imposed mean flow. |
Sunday, November 19, 2023 5:40PM - 5:53PM |
J17.00006: Melting of ice balls in homogeneous isotropic turbulence Edoardo Bellincioni, Sander Huisman, Detlef Lohse We study the melting of thermalised large-scale ice balls in different turbulence intensities. For this a dodecahedral water tank of about 210 litres is fitted with twenty numerically-controlled electric motors mounted on the vertices, which agitate the water with impellers, reaching Reynolds numbers of 10^{6}. Zero-mean velocity homogeneous isotropic turbulence (0MVHIT) is achieved in an approximately 20 cm diameter volume in the centre of the dodecahedron. A hole in the top part of the tank allows particles up to 15 cm diameter to be inserted in the tank. The silhouettes of the ice balls are captured with shadowgraphy. We studied the conductive heat transfer from the turbulent water to the ice ball. We found that the Nusselt number is constant throughout the melting process, and Nu and Re are related through a power-law. The ice balls melt isotropically, maintaining sphericity. To better describe the interaction between the turbulent flow and the (melting) ball we investigated the flow with both PIV and numerical simulations. |
Sunday, November 19, 2023 5:53PM - 6:06PM |
J17.00007: Heat Transfer in the Wake of a Sectionally Heated Infinite Square Bluff Body Sai Abhideep Pundla, Vivek C Nair, Pratik Bansode, Kapil Aryal, Brian Dennis, Dereje Agonafer Bluff bodies are objects or structures with a non-streamlined shape that interact with some fluid flow and create complex flow patterns in their wake. Large bluff body structures with heating on multiple sides are common in human society. The heat transfer due to the wake of such structures directly affects the downstream environment and, as such, is of interest to researchers. Flow past bluff bodies and heated bluff bodies has been widely studied - This work expands on pervious research by numerically studying the heat transfer in the wake of a sectionally heated infinite square bluff body. The simulations are run at Reynolds number Re 750 and result in a wake that transitions to turbulent flow past the recirculation region. The bluff body is split into five sections in the spanwise axis and varying patterns of temperature differential is applied to the sections and their sides. The presentation will discuss the heat transfer characteristics, and heat dispersal patterns in the wake. |
Sunday, November 19, 2023 6:06PM - 6:19PM |
J17.00008: Destruction of advective heat flux by toroidal flow in a non-rotating internally heated full sphere Tobias Sternberg, Andrew Jackson We study thermal convection in a non-rotating internally heated full sphere at a Prandtl number of unity with fixed temperature boundary conditions using 3D Direct Numerical Simulations. The onset mode of this system is purely poloidal, steady-state and has spherical harmonic degree l=1 both for stress-free and no-slip boundary conditions. As the Rayleigh number is increased to slightly supercritical values, the poloidal flow intensifies, but no toroidal flow is produced. We analytically demonstrate the existence of a large class of poloidal modes whose non-linear interactions do not generate toroidal flow. The onset of toroidal flow occurs as a secondary instability at roughly 10Ra_{c}. In the case of stress-free boundary conditions, this leads to a decrease in the Nusselt number measuring the strength of advective heat flux. The resulting flow is still steady-state. As the Rayleigh number is increased further, there is a range of the Rayleigh number over which the share of kinetic energy of the toroidal flow continues to grow and the Nusselt number continues to decrease. We believe that this effect, which occurs only for stress-free boundary conditions, has not been demonstrated before in 3D simulations. |
Sunday, November 19, 2023 6:19PM - 6:32PM Author not Attending |
J17.00009: Abstract Withdrawn |
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