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Full-Text Articles in Engineering
Sensitivity Analysis Of Frost Deposition In Turbulent Flow Over A Cold Plate Using Direct Numerical Simulation, N. Farzaneh, Nadim Zgheib, S. A. Sherif, S. Balachandar
Sensitivity Analysis Of Frost Deposition In Turbulent Flow Over A Cold Plate Using Direct Numerical Simulation, N. Farzaneh, Nadim Zgheib, S. A. Sherif, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We use a recently-developed, turbulence-informed physics-based model to study frost buildup over a flat plate subjected to turbulent flow. The plate temperature is held fixed but varied across simulations in the range −10◦C ≤ T∗ p ≤ −5◦C. Similarly, the free-stream temperature and humidity ratio are also held fixed but varied across simulations in the range 0◦C ≤ T∗∞ ≤ 20◦C and 3.77 × 10−3 ≤ ew∞ ≤ 1.47×10−2, respectively. We find the Nusselt and Sherwood numbers, when scaled by the frost surface to free stream temperature and humidity ratio difference, respectively, to become independent of free-stream temperature and humidity …
A Physics-Based Model For Frost Buildup Under Turbulent Flow Using Direct Numerical Simulations, Nadim Zgheib, N. Farzaneh, S. Balachandar, S. A. Sherif
A Physics-Based Model For Frost Buildup Under Turbulent Flow Using Direct Numerical Simulations, Nadim Zgheib, N. Farzaneh, S. Balachandar, S. A. Sherif
Mechanical Engineering Faculty Publications and Presentations
We present a new model for frost buildup under turbulent (and laminar) flow using direct numerical simulations. The physical model consists of two layers, the air and the frost. The air layer is fully resolved and consists of solving for the velocity, temperature, and vapor mass fraction fields. The frost layer thickness is resolved using conservation of mass and energy. Both phases are dynamically coupled using the immersed boundary method. Three-dimensional simulations are conducted in an open-channel configuration. A number of challenges need to be overcome to make these simulations feasible. First, to enforce far-field conditions of zero …
On The Role Of Sidewalls In The Transition From Straight To Sinuous Bedforms, Nadim Zgheib, S. Balachandar
On The Role Of Sidewalls In The Transition From Straight To Sinuous Bedforms, Nadim Zgheib, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results from direct numerical simulation on the transition from straight-crested to sinuous-crested bedforms. The numerical setup is representative of turbulent open channel flow over an erodible sediment bed at a shear Reynolds number of Reτ = 180. The immersed boundary method accounts for the presence of the bed. The simulations are two-way coupled such that the turbulent flow can erode and modify the bed, and in turn, the bed modifies the overlying flow. Coupling from the flow to the bed occurs through the Exner equation, while back coupling from the bed to the flow is achieved by …
Linear Stability Analysis Of Subaqueous Bedforms Using Direct Numerical Simulations, Nadim Zgheib, S. Balachandar
Linear Stability Analysis Of Subaqueous Bedforms Using Direct Numerical Simulations, Nadim Zgheib, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results on the formation of ripples from linear stability analysis. The analysis is coupled with direct numerical simulations of turbulent open-channel flow over a fixed sinusoidal bed. The presence of the sediment bed is accounted for using the immersed boundary method. The simulations are used to extract the bed shear stress and consequently the sediment transport rate. The approach is different from traditional linear stability analysis in the sense that the phase lag between the bed topology and the sediment flux is obtained from the three-dimensional turbulent simulations. The stability analysis is performed on the Exner equation, whose …
Suspension-Driven Gravity Surges On Horizontal Surfaces: Effect Of The Initial Shape, Nadim Zgheib, T. Bonometti, S. Balachandar
Suspension-Driven Gravity Surges On Horizontal Surfaces: Effect Of The Initial Shape, Nadim Zgheib, T. Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results from highly resolved direct numerical simulations of canonical (axisymmetric and planar) and non-canonical (rectangular) configurations of horizontal suspension-driven gravity surges. We show that the dynamics along the initial minor and major axis of a rectangular release are roughly similar to that of a planar and axisymmetric current, respectively. However, contrary to expectation, we observe under certain conditions the final extent of the deposit from finite releases to surpass that from an equivalent planar current. This is attributed to a converging flow of the particle-laden mixture toward the initial minor axis, a behaviour that was previously reported for …
Direct Numerical Simulation Of Cylindrical Particle-Laden Gravity Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Direct Numerical Simulation Of Cylindrical Particle-Laden Gravity Currents, Nadim Zgheib, Thomas Bonometti, S. Balachandar
Mechanical Engineering Faculty Publications and Presentations
We present results from direct numerical simulations (DNS) of cylindrical particle-laden gravity currents. We consider the case of a full depth release with monodisperse particles at a dilute concentration where particle–particle interactions may be neglected. The disperse phase is treated as a continuum and a two-fluid formulation is adopted. We present results from two simulations at Reynolds numbers of 3450 and 10,000. Our results are in good agreement with previously reported experiments and theoretical models. At early times in the simulations, we observe a set of rolled up vortices that advance at varying speeds. These Kelvin–Helmholtz (K–H) vortex tubes are …