Investigations of the linear and non-linear flow harmonics using the A Multi-Phase Transport model

The Multi-Phase Transport model (AMPT) is used to study the effects of the parton-scattering cross-sections ($\sigma_{pp}$) and hadronic re-scattering on the linear contributions to the flow harmonic \fourth, the non-linear response coefficients, and the correlations between different order flow symmetry planes in Au+Au collisions at 200~GeV. The model results, which agree with current experimental measurements, indicate that the higher-order flow harmonics are sensitive to the $\sigma_{pp}$ variations. However, the non-linear response coefficients and the correlations between different order flow symmetry planes are $\sigma_{pp}$ independent. These results suggest that further detailed experimental measurements which span a broad range of collision systems and beam energies could serve as an additional constraint for the theoretical models' calculations.

Flow Symmetry and Heat Transfer Characteristics of Winglet Vortex Generators Arranged in Common Flow up Configuration

The generation of longitudinal vortices is an effective method for promoting thermal performance with a relative low-pressure penalty in heat exchangers. The winglet pair can generate symmetrical longitudinal vortices on the cross-section of the channel. The heat transfer and pressure-loss characteristics of a pair of winglet vortex generators with different transverse pitches are numerically studied in this paper. The winglet pair arranged in a common flow up configuration generates a pair of symmetrical longitudinal main vortices with counter-rotating directions. The symmetrical flow structure induces fluid to flow from the bottom towards the top of the channel in the common flow region between the longitudinal vortices. The flow symmetry of the longitudinal vortices and the heat transfer performance are strongly affected by the transverse pitch of the winglet pair owing to the interaction between the longitudinal vortices. The optimal transverse pitch of the studied winglet pair with the best thermal performance is reported. The increments in the vortex intensity and the Nusselt number for the optimal pitch are increased by up to 21.4% and 29.2%, respectively.

Characteristics of Flow Symmetry and Heat Transfer of Winglet Pair in Common Flow Down Configuration

The effect of transverse pitch between a pair of delta-winglet vortex generators arranged in a common flow down configuration on the symmetrical flow structure and heat-transfer performance was numerically investigated. The results showed that symmetrical longitudinal vortices form a common flow down region between the vortices. The fluid is induced to flow from the top towards the bottom of the channel in the common flow region, which is advantageous to the heat transfer of the bottom fin. The vortex interaction increases and the vortex intensity decreases along with the decrease in transverse pitch of vortex generators. Vortex interaction has a slight influence on pressure penalty. The Nusselt number decreases with increasing vortex interaction. The vortices gradually attenuate and depart from each other during the process of flowing downward. A reasonable transverse pitch of delta-winglet vortex generators in a common-flow-down configuration is recommended for high thermal performance.

Impact of Nonlinear Thermal Radiation on the Time-Dependent Flow of Non-Newtonian Nanoliquid over a Permeable Shrinking Surface

Symmetry and fluid dynamics either advances the state-of-the-art of mathematical methods and extends the limitations of existing methodologies to new contributions in fluid. Physical scenario is modelled in terms of differential equations as mathematical models in fluid mechanics to address current challenges. In this work a physical problem to examine the unsteady flow of a third-grade non-Newtonian liquid induced through a permeable shrinking surface containing nanoliquid is considered. The model of Buongiorno is utilized comprising the thermophoresis and Brownian effects through nonlinear thermal radiation and convective condition. Based on the flow symmetry, suitable similarity transformations are employed to alter the partial differential equations into nonlinear ordinary differential equations and then these ordinary differential equations are numerically executed via three-stage Lobatto IIIa formula. The flow symmetry is discussed for interesting physical parameters and thus this work is concluded. More exactly, the impacts of pertinent constraints on the concentration, temperature and velocity profiles along together drag force, Sherwood and Nusselt numbers are explained through the aid of the tables and plots. The outcomes reveal that the dual nature of solutions is gained for a specific amount of suction and flow in the decelerating form A < 0 . However, the unique result is obtained for flow in accelerating form A ≥ 0 . In addition, the non-linear parameter declines the liquid velocity and augments the concentration and temperature fields in the first result, whereas the contrary behavior is scrutinized in the second result.

Simulations for Flow-Symmetry Through r.avaflow in the General Two-Phase Mass Flow Model

Gravitational flows, e.g., landslide, debris flow and avalanches are hazardous mass wasting processes. The proper understanding of their dynamics is very important. As laboratory experiments can not perfectly model their initiation process and field assess of the live events are very difficult, numerical experiments have become the promising way for the study of their flow dynamics. Here we employ the enhanced version of two-phase mass flow model [33] through the open source computational code, r.avaflow to analyze the issue of symmetry in the flow. Two-phase debris mass are triggered from all the flanks of the three different pyramids (triangle-based, square-based and octagon-based) with different rotational symmetry and study the flow pattern along with maximum kinetic energy of the flow. Flow past two different types of obstacles (a tetrahedron and a square based pyramid) are also observed. The possible causes of asymmetry in the flow are also analyzed.

Study of Angle-of-Attack (AoA) for Airfoil in Deterministic Lateral Displacement (DLD)

Deterministic lateral displacement (DLD) is a method of inertial size-based particle separation with potential applications in high throughput sample processing, such as the fractionation of blood or the purification of target species like viral particles or circulating tumor cells. Recently, it has been shown that symmetric airfoils with neutral angle-of-attack (AoA) can be used for high-throughput design of DLD device, due to their mitigation of vortex effects and preservation of flow symmetry under high Reynolds number (Re) conditions. While high-Re operation with symmetric airfoils has been established, the effect of AoA for airfoil on the DLD performance has not been characterized. In this study, we present a high-Re investigation with symmetric airfoil-shaped pillars having positive and negative 15 degree AoA. Both positive and negative AoA configurations yield significant flow anisotropy at higher flow rates. The stronger shift of the critical diameter (Dc) was observed with negative AoA, but not in positive AoA device. The most likely contributor may be the growing anisotropy that develops in the AoA device at higher flow rates. This study shows that high-Re DLD design with airfoil shaped pillars requires significant consideration for pillar orientation to control flow symmetry.

How drag force evolves in global common envelope simulations

ABSTRACT We compute the forces, torque, and rate of work on the companion-core binary due to drag in global simulations of common envelope (CE) evolution for three different companion masses. Our simulations help to delineate regimes when conventional analytic drag force approximations are applicable. During and just prior to the first periastron passage of the in-spiral phase, the drag force is reasonably approximated by conventional analytic theory and peaks at values proportional to the companion mass. Good agreement between global and local 3D ‘wind tunnel’ simulations, including similar net drag force and flow pattern, is obtained for comparable regions of parameter space. However, subsequent to the first periastron passage, the drag force is up to an order of magnitude smaller than theoretical predictions, quasi-steady, and depends only weakly on companion mass. The discrepancy is exacerbated for larger companion mass and when the inter-particle separation reduces to the Bondi–Hoyle–Lyttleton accretion radius, creating a turbulent thermalized region. Greater flow symmetry during this phase leads to near balance of opposing gravitational forces in front of and behind the companion, hence a small net drag. The reduced drag force at late times helps explain why companion-core separations necessary for envelope ejection are not reached by the end of limited duration CE simulations.

Reeb flow symmetry on 3-dimensional almost paracosymplectic manifolds

Mainly, we prove that the Ricci operator Q of an 3-dimensional almost paracosymplectic manifold M is invariant along the Reeb flow, that is M satisfies L?Q = 0 if and only if M is an almost paracosymplectic k-manifold with k ? -1.