Computational Analysis of the Rotating Cylinder Embedment onto Flat Plate

The Magnus effect and its evolution have greatly affected the aerospace industry over the past century to date. Nevertheless, cylinder embedment onto a flat plate offers a new discovery that is yet to be investigated, specifically whether the concept could enhance the aerodynamic properties of the flat plate following the Magnus effect momentum injection. Over the past decade, the use of a rotating cylinder on an aerofoil has existed from past researches studies where the embedment has significantly increased in its aerodynamic performance better than the one without Magnus application. However, it would be hard to achieve experimental-wise as an accurate measurement and fabrication would be needed to have the same resulting effects. Here, most of the researchers would not focus deeply on the placement of the cylinder as this may increase their fabrication and testing complications. Therefore, the current study delineates the use of flat plate as the foundation design to encounter the arise matter by reducing its complication yet easy to manufacture experimentally. In this work, the model output was evaluated by using ANSYS WORKBENCH 2019 software to simulate two-dimensional flow analysis for the rotational velocities of 500 RPM and 1000 RPM, respectively. This was done for different Reynolds numbers ranging from 4.56E+05 to 2.74E+06 which implicitly implied with free stream velocities varying from 5 m/s to 30 m/s for different angles of attack between 0 to 20 degrees. Prior to developing the best model embedment, the mesh independency test was validated with an error of less than 1%. The study resulted in a remarkable trend that was noticeably up to 32% (500 RPM) and 76% (1000 RPM) better in compared to the one without momentum injection. Similarly, the high recovery led to a tremendously lower of 51% (500 RPM) and 99% (1000 RPM), respectively. In sum, these findings generated a stall angle delay of up to 26% (500 RPM) and 78% (1000 RPM) accordingly.

Learning efficient navigation in vortical flow fields

Efficient point-to-point navigation in the presence of a background flow field is important for robotic applications such as ocean surveying. In such applications, robots may only have knowledge of their immediate surroundings or be faced with time-varying currents, which limits the use of optimal control techniques. Here, we apply a recently introduced Reinforcement Learning algorithm to discover time-efficient navigation policies to steer a fixed-speed swimmer through unsteady two-dimensional flow fields. The algorithm entails inputting environmental cues into a deep neural network that determines the swimmer’s actions, and deploying Remember and Forget Experience Replay. We find that the resulting swimmers successfully exploit the background flow to reach the target, but that this success depends on the sensed environmental cue. Surprisingly, a velocity sensing approach significantly outperformed a bio-mimetic vorticity sensing approach, and achieved a near 100% success rate in reaching the target locations while approaching the time-efficiency of optimal navigation trajectories.

An experimental test of the Mocikat-Herwig theory of local turbulent heat transfer measurements on cold objects

Experimental results are presented of a test of the theory of local turbulent heat transfer measurements proposed by Mocikat and Herwig in 2007. A miniaturized multi-layer heat transfer sensor was developed and employed in this study. The new heat transfer sensor was designed to work in air and liquids, and this capability enabled the simultaneous investigation of different Prandtl numbers. Two basic configurations, namely the flow past a blunt plate and the flow past an inclined square cylinder, were investigated in test sections of wind and water tunnels. Convective heat transfer coefficients were obtained through conventional testing (i.e., employing thoroughly heated test objects) and using the new miniaturized sensor approach (i.e., utilizing cold test objects without heating). The main prediction of the Mocikat-Herwig theory that a specific thermal adjustment coefficient of the employed actual miniaturized heat transfer sensor should exist in the fully turbulent flow regime was proven for developed two-dimensional flow. The observed effect of the Prandtl number on this coefficient was in good agreement with the prediction of the asymptotic expansion method. The square cylinder results indicated the inherent limits of the local turbulent heat transfer measurement approach, as suggested by Mocikat and Herwig.

Flow theory: Advancing the two-dimensional conceptualization

This research advances the conceptualization and measurement of flow. The results of six studies (N = 2809) reveal that flow has two dimensions: “fluency,” which is comprised of experiences related to fluent thought and action; and “absorption,” which is based on sustained full attention. The results also demonstrate that the two dimensions have nuanced relationships with other variables. Specifically, while the fluency dimension is related to antecedents of flow (familiarity, skill, progress), the absorption dimension is not. Conversely, the absorption dimension was found to be strongly related to consequences of flow (behavioral intentions, presence), while the fluency dimension was not. Furthermore, we demonstrate that fluency-related experiences can give rise to the absorption-related experiences, which advances our understanding of how flow emerges. Finally, we develop a refined measure of flow called the two-dimensional-flow scale, and demonstrate its enhanced ability to capture variance in flow and other related variables in leisure contexts.

Networked configurations as an emergent property of transverse aeolian ridges on Mars

Transverse aeolian ridges – enigmatic Martian features without a proven terrestrial analog – are increasingly important to our understanding of Martian surface processes. However, it is not well understood how the relationships between different ridges evolve. Here we present a hypothesis for the development of complex hexagonal networks from simple linear forms by analyzing HiRISE images from the Mars Reconnaissance Orbiter. We identify variable morphologies which show the presence of secondary ridges, feathered transverse aeolian ridges and both rectangular and hexagonal networks. We propose that the formation of secondary ridges and the reactivation of primary ridge crests produces sinuous networks which then progress from rectangular cells towards eventual hexagonal cells. This morphological progression may be explained by the ridges acting as roughness elements due to their increased spatial density which would drive a transition from two-dimensional bedforms under three-dimensional flow conditions, to three-dimensional bedforms under two-dimensional flow conditions.

Analysis of Performance of Cavitation Models with Analytically Calculated Coefficients

Cavitation is often simulated using a mixture model, which considers the transport of an active scalar, namely the vapor fraction αv. Source and sink terms of the transport equation of αv, namely vaporization and condensation terms, rule the dynamics of the cavity and are described through different models. These models contain empirical coefficients generally calibrated through optimization processes. The purpose of this paper is to propose an analytical approach for the calculation of the coefficients, based on the time scales of vaporization and condensation processes. Four different models are compared considering as a test-case a two-dimensional flow around a cylinder. Some relevant quantities are analyzed both for standard value of coefficients, as found in the literature, and the coefficients calculated through the analytical approach. The study shows that the analytical computation of the coefficients of the model substantially improve the results, and the models considered give similar results, both in terms of cavitation regime and mean vapor fraction produced.

A SEMI-ANALYTICAL METHOD FOR A FLOW OF NON-VISCOUS FLUID AROUND AN AIRFOIL WITH A SHARP TRAILING EDGE

In the present work we propose a method to study a two-dimensional flow of non-viscous fluid around an airfoil with a sharp trailing edge, by the double-layer potential theory. The circulation of velocity vector is modeled by the potential of a point vortex whose center is located inside the boundary contour. The magnitude of the circulation is defined on the basis of the Joukowski-Chaplygin postulate. There are presented some results for a Joukowski rudde, as well as for the airfoil in the form of a pair of interacting circles. It is performed a comparison of the circulation with its theoretical value.

Large eddy simulation of converging Richtmyer–Meshkov instability based on subgrid-scale dissipation similar method

This paper focuses on large eddy simulation of the Richtmyer–Meshkov instability (RMI) in spherical and cylindrical converging geometries with a Mach number [Formula: see text] based on subgrid-scale (SGS) dissipation similar method (SDSM). Based on the converging RMI problem, we obtain from a priori test and theoretical analysis that the suggested method can provide accurate structural correlation while ensuring the computational stability. Comparing the numerical simulation results with direct numerical simulation (DNS) and existing model in converging RMI problem, we could find that the suggested method overcomes some defects of the existing model, such as the Smagorinsky model cannot predict transition accurately and the helicity model can only predicts the quasi-two-dimensional flow precisely. It provides a beneficial tool for the research of converging RMI.