Katepalli R. Sreenivasan
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Small-scale properties from exascale computations of turbulence on a $\mathbf{32\,768^3}$ periodic cube Open
View article: Hierarchical network of thermal plumes and their dynamics in turbulent Rayleigh–Bénard convection
Hierarchical network of thermal plumes and their dynamics in turbulent Rayleigh–Bénard convection Open
The link between characteristic coherent structures and their statistical properties in turbulent flows remains largely unclear and is thus a central bottleneck for a better understanding of turbulent flows. Here, we demonstrate this link …
View article: A brief perspective on fluid mechanics research
A brief perspective on fluid mechanics research Open
This article presents my personal perspective on fluid mechanics research as it has evolved over the years, with a few specific references to the Division of Fluid Dynamics of the American Physical Society and its relation to the Physics o…
View article: Transient and steady convection in two dimensions
Transient and steady convection in two dimensions Open
We simulate thermal convection in a two-dimensional square box using the no-slip condition on all boundaries, and isothermal bottom and top walls, and adiabatic sidewalls. We choose 0.1 and 1 for the Prandtl number $Pr$ and vary the Raylei…
View article: Compact quantum algorithms for time-dependent differential equations
Compact quantum algorithms for time-dependent differential equations Open
Many claims of computational advantages have been made for quantum computing over classical but they have not been demonstrated for practical problems. Here, we present algorithms for solving time-dependent PDEs, with particular reference …
View article: Compact quantum algorithms for time-dependent differential equations
Compact quantum algorithms for time-dependent differential equations Open
Many claims of computational advantages have been made for quantum computing over classical but they have not been demonstrated for practical problems. Here, we present algorithms for solving time-dependent PDEs, with particular reference …
View article: Roddam Narasimha. 20 July 1933—14 December 2020
Roddam Narasimha. 20 July 1933—14 December 2020 Open
Roddam Narasimha’s scientific research in fluid dynamics encompassed turbulent flows—including the transition from the laminar state to turbulence and vice versa —kinetic theory of gases and structure of shock waves, nonlinear dynamics, as…
View article: Multiscale circulation in wall-parallel planes of turbulent channel flows
Multiscale circulation in wall-parallel planes of turbulent channel flows Open
Wall turbulence consists of various sizes of vortical structures that induce flow circulation around a wide range of closed Eulerian loops. Here we investigate the multiscale properties of circulation around such loops in statistically hom…
View article: Radial Flow Component of Sun’s High-frequency Retrograde Inertial Waves
Radial Flow Component of Sun’s High-frequency Retrograde Inertial Waves Open
Solar inertial modes have the potential to surpass the diagnostic capabilities of acoustic waves in probing the deep interior of the Sun. The fulfillment of this potential requires an accurate identification and characterization of these m…
View article: Bounded dissipation law and profiles of turbulent velocity moments in wall flows
Bounded dissipation law and profiles of turbulent velocity moments in wall flows Open
Understanding the effects of solid boundaries on turbulent fluctuations remains a long-standing challenge. Available data on mean-square fluctuations in these flows show apparent contradiction with classical scaling. We had earlier propose…
View article: Radial flow component of Sun's high frequency retrograde inertial waves
Radial flow component of Sun's high frequency retrograde inertial waves Open
Solar inertial modes have the potential to surpass the diagnostic capabilities of acoustic waves in probing the deep interior of the Sun. The fulfillment of this potential requires an accurate identification and characterization of these m…
View article: What Is the Turbulence Problem, and When May We Regard It as Solved?
What Is the Turbulence Problem, and When May We Regard It as Solved? Open
Turbulent motion of fluids is often thought of as a grand problem, but what exactly is this “turbulence problem”? Because it has often been proclaimed as very difficult and unsolved, when can we claim that it is solved? How does this situa…
View article: Multiscale circulation in wall-parallel planes of turbulent channel flows
Multiscale circulation in wall-parallel planes of turbulent channel flows Open
Wall turbulence consists of various sizes of vortical structures that induce flow circulation around a wide range of closed Eulerian loops. Here we investigate the multiscale properties of circulation around such loops in statistically hom…
View article: Turbulent convection in rotating slender cells
Turbulent convection in rotating slender cells Open
Turbulent convection in the interiors of the Sun and the Earth occurs at high Rayleigh numbers $Ra$ , low Prandtl numbers $Pr$ , and different levels of rotation rates. To understand the combined effects better, we study rotating turbulent…
View article: Solar convective velocities: Updated helioseismic constraints
Solar convective velocities: Updated helioseismic constraints Open
Modeling heat transport by convection is one of the most challenging aspects of solar and stellar physics. The literature currently provides apparently inconsistent observational estimates of the strength of large-scale convective flows in…
View article: No sustained mean velocity in the boundary region of plane thermal convection
No sustained mean velocity in the boundary region of plane thermal convection Open
We study the dynamics of thermal and momentum boundary regions in three-dimensional direct numerical simulations of Rayleigh–Bénard convection for the Rayleigh-number range $10^5\leq Ra \leq 10^{11}$ and $Pr=0.7$ . Using a Cartesian slab w…
View article: Bistability in the sunspot cycle
Bistability in the sunspot cycle Open
A direct dynamical test of the sunspot cycle is carried out to indicate that a
stochastically forced nonlinear oscillator characterizes its dynamics. The sunspot series is then decomposed into its eigen time-delay coordinates. The rele…
View article: Simulating fluid flows with quantum computing
Simulating fluid flows with quantum computing Open
The applications and impact of high fidelity simulation of fluid flows are far-reaching. They include settling some long-standing and fundamental questions in turbulence. However, the computational resources required for such efforts are e…
View article: Saturation of exponents and the asymptotic fourth state of turbulence
Saturation of exponents and the asymptotic fourth state of turbulence Open
A recent discovery about the inertial range of homogeneous and isotropic turbulence is the saturation of the scaling exponents ζn for large n, defined via structure functions of order n as Sn(r)=〈(δru)n〉=A(n)rζn. We focus on longitudinal s…
View article: Two quantum algorithms for solving the one-dimensional advection–diffusion equation
Two quantum algorithms for solving the one-dimensional advection–diffusion equation Open
Two quantum algorithms are presented for the numerical solution of a linear one-dimensional advection–diffusion equation with periodic boundary conditions. Their accuracy and performance with increasing qubit number are compared point-by-p…
View article: Bounded dissipation law and profiles of turbulent velocity moments in wall flows
Bounded dissipation law and profiles of turbulent velocity moments in wall flows Open
Turbulent wall flows offer the most direct means for understanding the effects of boundaries and viscosity on turbulent fluctuations. Available data on mean-square fluctuations in these flows show apparent contradiction with classical scal…
View article: Bistability in the sunspot cycle
Bistability in the sunspot cycle Open
A direct dynamical test of the sunspot-cycle is carried out which indicates that a stochastically forced non-linear oscillator characterizes its dynamics. The sunspot series is then decomposed into its eigen time-delay coordinates. The ana…
View article: A Linear Model for Inertial Modes in a Differentially Rotating Sun
A Linear Model for Inertial Modes in a Differentially Rotating Sun Open
Inertial wave modes in the Sun are of interest owing to their potential to reveal new insight into the solar interior. These predominantly retrograde-propagating modes in the solar subsurface appear to deviate from the thin-shell Rossby–Ha…
View article: No sustained mean velocity in the boundary region of plane thermal convection
No sustained mean velocity in the boundary region of plane thermal convection Open
We study the dynamics of thermal and momentum boundary regions in three-dimensional direct numerical simulations of Rayleigh-Bénard convection for the Rayleigh number range $10^5 \le Ra \le 10^{11}$ and $Pr=0.7$. Using a Cartesian slab wit…
View article: Phenomenology of transition to quantum turbulence in flows of superfluid helium
Phenomenology of transition to quantum turbulence in flows of superfluid helium Open
Transition from laminar to turbulent states of classical viscous fluids is complex and incompletely understood. Transition to quantum turbulence (QT), by which we mean the turbulent motion of quantum fluids such as helium II, whose physica…
View article: Average turbulence dynamics from a one-parameter kinetic theory: Estimation of the relaxation time
Average turbulence dynamics from a one-parameter kinetic theory: Estimation of the relaxation time Open
We provide a theoretical estimation of the relaxation time for the kinetic theoretical representation of homogeneous, isotropic, and stationary turbulent flow. The basic approach depends on the construction of a balance of fluctuation and …
View article: Two quantum algorithms for solving the one-dimensional advection-diffusion equation
Two quantum algorithms for solving the one-dimensional advection-diffusion equation Open
Two quantum algorithms are presented for the numerical solution of a linear one-dimensional advection-diffusion equation with periodic boundary conditions. Their accuracy and performance with increasing qubit number are compared point-by-p…
View article: Reynolds number required to accurately discriminate between proposed trends of skin friction and normal stress in wall turbulence
Reynolds number required to accurately discriminate between proposed trends of skin friction and normal stress in wall turbulence Open
In Nagib, Chauhan and Monkewitz~\cite{NCM07} we concluded that nearly all available $C_f$ relations for zero-pressure-gradient boundary layers are in remarkable agreement over the entire range $Re_θ$ $<$ O($10^8$), provided one coefficient…
View article: Hybrid quantum algorithms for flow problems
Hybrid quantum algorithms for flow problems Open
For quantum computing (QC) to emerge as a practically indispensable computational tool, there is a need for quantum protocols with end-to-end practical applications—in this instance, fluid dynamics. We debut here a high-performance quantum…
View article: Reynolds number asymptotics of wall-turbulence fluctuations
Reynolds number asymptotics of wall-turbulence fluctuations Open
In continuation of our earlier work (Chen & Sreenivasan, J. Fluid Mech. , vol. 908, 2021, R3; Chen & Sreenivasan, J. Fluid Mech. , vol. 933, 2022 a , A20 – together referred to as CS hereafter), we present a self-consistent Reynolds number…