Predicting unsteady heat transfer effect of vehicle thermal management system using steady velocity equivalent method

In the process of vehicle development, the unsteady simulation of thermal management system is very important. A 3D-CFD calculation model of vehicle thermal management is established, and simulations were undertaken for uphill with full loads operations condition. The steady results show that the surface heat transfer coefficient increases to the quadratic parabolic relationship. The unsteady results show that the pulsating temperatures of exhaust and external airflow are higher than about 50°C and lower than 10°C, respectively, and the heat dissipating capacities are higher than about 11%. Accordingly, the conversion equivalent exhaust velocity increased by 1.67%, and the temperature distribution trend is basically the same as unsteady results. The comparison results show that the difference in the under-hood should be not noted, and that the predicted exhaust system surface temperatures using steady velocity equivalent method are low less 10°C than the unsteady results. These results show the steady velocity equivalent method can be used to predict the unsteady heat transfer effect of vehicle thermal management system, and the results obtained by this method are basically consistent with the unsteady results. It will greatly save computing resources and shorten the cycle in the early development of the vehicle thermal management system.

Low-frequency electroencephalogram oscillations govern left-eye lateralization during anti-predatory responses in the music frog

ABSTRACTVisual lateralization is widespread for prey and anti-predation in numerous taxa. However, it is still unknown how the brain governs this asymmetry. In this study, we conducted behavioral and electrophysiological experiments to evaluate anti-predatory behaviors and dynamic brain activities in Emei music frogs (Nidirana daunchina), to explore the potential eye bias for anti-predation and the underlying neural mechanisms. To do this, predator stimuli (a model snake head and a leaf as a control) were moved around the subjects in clockwise and anti-clockwise directions at steady velocity. We counted the number of anti-predatory responses and measured electroencephalogram (EEG) power spectra for each band and brain area (telencephalon, diencephalon and mesencephalon). Our results showed that (1) no significant eye preferences could be found for the control (leaf); however, the laterality index was significantly lower than zero when the predator stimulus was moved anti-clockwise, suggesting that left-eye advantage exists in this species for anti-predation; (2) compared with no stimulus in the visual field, the power spectra of delta and alpha bands were significantly greater when the predator stimulus was moved into the left visual field anti-clockwise; and, (3) generally, the power spectra of each band in the right-hemisphere for the left visual field were higher than those in the left counterpart. These results support that the left eye mediates the monitoring of a predator in music frogs and lower-frequency EEG oscillations govern this visual lateralization.

Real power loss diminution by predestination of particles wavering search algorithm

In this work Predestination of Particles Wavering Search (PPS) algorithm has been applied to solve optimal reactive power problem. PPS algorithm has been modeled based on the motion of the particles in the exploration space. Normally the movement of the particle is based on gradient and swarming motion. Particles are permitted to progress in steady velocity in gradient-based progress, but when the outcome is poor when compared to previous upshot, immediately particle rapidity will be upturned with semi of the magnitude and it will help to reach local optimal solution and it is expressed as wavering movement. In standard IEEE 14, 30, 57,118,300 bus systems Proposed Predestination of Particles Wavering Search (PPS) algorithm is evaluated and simulation results show the PPS reduced the power loss efficiently.

Steady Streaming Induced by Asymmetric Oscillatory Flows over a Rippled Bed

The flow induced by progressive water waves propagating over a rippled bed is reproduced by means of the numerical solution of momentum and continuity equations to gain insights on the steady streaming induced in the bottom boundary layer. When the pressure gradient that drives the flow is given by the sum of two harmonic components an offshore steady streaming is generated within the boundary layer which persists in the irrotational region. This steady streaming depends on the Reynolds number and on the geometrical characteristics of the ripples. Nothwithstanding the presence of a steady velocity component, the time-average of the force on the ripples vanishes.

Estimation of flow velocity for a debris flow via the two-phase fluid model

The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate the velocity for a debris flow.

Estimation of flow velocity for a debris flow via the two-phase fluid model

The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

Velocity-Toughening and Crack Speed Oscillations in the Dynamic Fracture of PMMA Plates

To study the propagating behavior of a dynamic crack in brittle materials, an experimental technique was developed that measures the propagation speed of a fast crack in a preloaded brittle strip. The specimen is a rectangular PMMA plate clamped by two heavy steel fixtures that are attached to a MTS test machine. After the specimen was tensile loaded to a prescribed load level, a sharp crack was initiated at the middle point on one side of the specimen. Due to the brittleness of the material, the crack propagates quickly across the specimen. The propagation velocity of the crack was measured by using the equally spaced conductive lines that were painted on the specimen surface before the tests. High speed video camera was also used for monitoring the propagation behavior of the cracks. The experimental results show that for each preloaded plate, the crack arrives at a steady velocity v0 after a short acceleration stage. In the steady stage crack propagation is in self-similar state. The steady velocity of the crack was found to be an increasing function of the energy Gc stored in the preloaded strip, which means that the material has a "velocity-toughening" property. When the crack speed exceeds a threshold, the crack exhibits apparent speed oscillations. This speed oscillation corresponds to the occurrence of the periodic grooves on the fractured surface. Further increase of the preload results in the bending, micro branching, and full bifurcations of the crack paths.

The aerodynamic performance of the feathertail glider, Acrobates pygmaeus (Marsupialia: Acrobatidae)

Photographic and videographic investigations of the aerodynamic performance of four captive adult Acrobates pygmeus are described. During short (1–4 m) glides, steep angles of descent (>45°) and large angles of attack (up to 50°) were used mid-flight, and the possums failed to achieve steady velocities. During longer (>10 m) glides steady velocities of 5.3–7.5 m s–1 were achieved, and glide angles of 21–42° and angles of attack between 36° and 45° were used. The best (lowest) glide angles used at steady velocity were similar to those documented in sugar gliders, but involved lower air speeds. During steady gliding the forelimbs of Acrobates assumed an ‘elbows-out’ disposition similar to that of Petauroides volans, and unlike that of petaurid gliders. A glide polar for Acrobates shows that it uses lower air speeds and higher sinking speeds than other gliding animals for which polars are available (several birds and one bat). Few data on the radius of turn and sinking speed were obtained; nevertheless, in accord with theory, sinking speeds were higher during tighter turns. During flight the feather-like tail was used to generate pitching movements and adjust the angle of attack and hence glide angle. However, the control of turns seems to be achieved primarily through limb adjustments.

Simulation of Facet Dendritic Shape of Isothermal Alloy in a Forced Flow by Phase Field Method

Numerical simulation based on a new regularized phase field model was performed to describe the dendritic growth of an isothermal alloy with a strong anisotropy in the presence of a forced flow. These results indicate that a crystal grow into an equiaxial facet dendritic in the absence of a forced flow and into an asymmetrical facet dendritic in the presence of a forced flow. With increasing a flow velocity, the tip steady velocity of upstream dendritic arm increases, that of the downstream arm decreases, and that of the perpendicular arms increases at first, and then decreases, the perpendicular arms gradually grow toward the incoming flow direction. In the certain range of anisotropy parameter, when γ is larger than 0.14, dendritic tip steady velocities in all direction are expected to reach their own saturation values. In addition, the effect of a compound forced flow on an isothermal facet dendritic is similar to experimental results.