Kinetic Energy Research Articles

Effect of abrasive volume fraction on energy utilization in suspension abrasive water jets based on VOF-DEM method

Suspension abrasive water jets (AWJs) rock breaking is the kinetic energy of abrasive particle group transport and transfer. However, it is difficult to be popularized and utilized due to the high energy consumption of rock breaking. In this study, the energy transfer rate in AWJs was focused on and was investigated using numerical and experimental methods. A two-way coupled algorithm was used to reproduce the oscillation characteristics of abrasive jets velocities, indicating that not only the abrasives' velocities but also the abrasives' distribution is crucial in energy transfer rate. Different dominant factors accounting for the abrasives' velocities and distribution were identified, and two parameters were proposed to account for the energy transfer process during the jet evolution process. The optimum abrasives' volume fraction was determined based on the evolution of the energy density and ratio of abrasive kinetic energy to the total energy, which was validated by rock breaking experiments. Increasing ratio of abrasive kinetic energy to the total energy by using the method of changing the volume fraction of the abrasive is an effective method to improve the rock breaking efficiency of suspension abrasive water jets.

Synchronization of networked mechanical systems without velocity information

AbstractThis paper studies the synchronization problem in a network of interconnected mechanical systems where the velocity information of the interacting agents is unavailable. To achieve this, a distributed law related to the kinetic and potential energies of the considered system is proposed. Specifically, by introducing an auxiliary system and a distributed filter, it is shown that the proposed algorithm enables the synchronization of the considered system by merely using the local position measurements. Moreover, it is also shown that, compared with the existing literature, the derived synchronization conditions are irrelevant to the eigenvalues of Laplacian matrix, thus circumventing the global information of the underlying system. Moreover, on condition that the absolute position information is available, it is also shown that apart from the synchronization of agents, the discrepancy between the position variable of the original system and that of the auxiliary variable tends to zero eventually. Finally, a concrete example and some comparisons are conducted to support the formulated setup and the obtained theoretical results.

Origami-Inspired Collapsible Structures for Small Rotorcraft Collision Resilience and Landing

Abstract This article reports on the design, fabrication, and testing of flexible, collapsible structures inspired by origami and kirigami that can be used to protect small rotorcraft from collision impacts and to serve as landing gear. Twenty structures created from variations of Pako Pako, Magic Ball, and Herringbone fold patterns were laser cut from cardstock and evaluated experimentally. Some of the Pako Pako structures were designed to have graduated mechanical stiffness. An empirical procedure based on acceleration measurements has been developed that enables quantitative evaluation of each structure based on the characterization parameters of peak acceleration, peak velocity, translational kinetic energy, impact duration, mass, and mechanical stiffness. Structures were mounted onto the front of a radio-controlled (RC) car and driven on a linear test track into a rigid wall. Accelerations measured during the collisions were numerically integrated to determine velocities over the impact and collapse/compression of the structures. Flight tests conducted with small RC quadcopters demonstrated that the collapsible structures could successfully be used to mitigate collisions, enough to enable the quadcopters to continue flying after a direct impact and to land indoors or on outdoor terrain with varying slopes and surfaces. Based on trade-off comparisons between the evaluative metrics of the cases studied, conical Pako Pako structures with uniform stiffness are shown to be the most effective for collision resilience and landing.

Stability and receptivity analyses of the heated flat-plate boundary layer with variable viscosity

This article presents the modal, non-modal, and resolvent analyses of the boundary layer developed over a heated flat-plate with temperature-dependent viscosity using linear stability theory. The governing equations are derived in the normal velocity–vorticity form by imposing small infinitesimal disturbances on the base flow with the Oberbeck-Boussinesq (OB) approximation. The spectral method is employed to discretize the governing stability equations in the wall-normal direction. The base flow comes from the similarity solution using R-K4th order method along with shooting techniques. The effects of viscosity stratification, inertia, shearing, and buoyancy on the stability of the boundary layer are investigated by varying the sensitivity parameter (ϵ), Reynolds (Re), Prandtl (Pr), and Richardson numbers (Ri). The modal analysis shows the time-asymptotic behavior of the disturbances and onset of instability is mainly caused by amplification of Tollmien–Schlichting (T-S) waves similar to as observe in the traditional Blasius case. The modal stability increases with increase in sensitivity parameter and stabilizing effects become more pronounced for liquid than gas. However, the thermal effects lead to destabilize the flow and strong destabilizing effects produced for higher Prandtl number. On the other hand, non-modal analysis displays an early transient growth of disturbances and an existence of these non-normality effects identified from the pseudospectra via. resolvent analysis. The non-modal growth increases with increase in ϵ even though T-S modes shift towards the damped region, which indicates the continuous modes in the eigenspectrum are more dominated than the discrete T-S modes due to the thermal effects. To clarify this qualitative change, a component-wise input–output analysis is performed to measure the receptivity to particular external disturbances. The results show the thermal energy of the disturbances is converted into kinetic energy due to thermal effects, resulting in strong receptivity amplification at the continuous mode due to the non-normality of the linear operator. Thus, the boundary layer under the influence of viscosity stratification, heating, and shearing effects is vulnerable to free-stream disturbances that could significantly affect bypass transition

Therapeutic Effect of Targeted Deployment Filling Coils in the Treatment of Intracranial Aneurysms.

Endovascular coil embolization is the primary therapeutic modality for intracranial aneurysms. Substantial reports have been found regarding the coil packing density and inflow jet. However, the hemodynamic effect of increasing the rate of tamponade in the inflow jet area within the aneurysm remains unclear. In this study, individualized geometries of six intracranial aneurysms were recruited: all six aneurysms were located in the internal carotid artery. Two groups were created by changing the position and orientation of the microcatheter for the release of the third segment of the filling coil. The finite element method was used to simulate coil deployment. Computational fluid dynamics was used to characterize hemodynamics in post-deployment aneurysms. The parameters evaluated included velocity reduction, wall shear stress (WSS), low WSS (LWSS), relative residence time (RRT), flow kinetic energy in the neck region of the aneurysms, and residual flow volume (RFV) in the aneurysms. At the peak time (t = 0.17 s), the targeted deployment group has similar proportion of LWSS area to conventional deployment groups: targeted 78.13% ± 34.59% versus normal 74.20% ± 36.94% (mean ± SD, p = 0.583). The targeted deployment group has a higher RRT area (targeted 16.84% ± 5.58% vs. normal 6.42% ± 5.67% [mean ± SD, p = 0.009]), smaller flow kinetic energy (targeted 9.43 ± 4.33 vs. normal 16.23 ± 5.92 [mean ± SD, p = 0.047]), and a larger RFV in the aneurysms (targeted 35.97 ± 24.35 mm3 vs. normal 25.80 ± 18.94 mm3 [mean ± SD, p = 0.44]). Inflow jets play an important role in the treatment of aneurysms, and deploying filling coils in accordance with inflow jets may result in a better hemodynamic environment.

Multi-channel machine learning based nonlocal kinetic energy density functional for semiconductors

Abstract The recently proposed machine learning-based physically-constrained nonlocal (MPN) kinetic energy density functional (KEDF) can be used for simple metals and their alloys (Sun and Chen 2024 Phys. Rev. B 109 115135). However, the MPN KEDF does not perform well for semiconductors. Here we propose a multi-channel MPN (CPN) KEDF, which extends the MPN KEDF to semiconductors by integrating information collected from multiple channels, with each channel featuring a specific length scale in real space. The CPN KEDF is systematically tested on silicon and binary semiconductors. We find that the multi-channel design for KEDF is beneficial for machine-learning-based models in capturing the characteristics of semiconductors, particularly in handling covalent bonds. In particular, the CPN5 KEDF, which utilizes five channels, demonstrates excellent accuracy across all tested systems. These results offer a new path for generating KEDFs for semiconductors.

Enhancement efficiency of flow and irreversibility system for MHD Buongiorno's nanofluid in complex peristaltic tapered channel with electroosmosis forces

Abstract Magnetohydrodynamic flow efficiency and irreversibility improvement research are multiple problems that arise when electroosmosis forces affect Buongiorno's nanofluid in a complicated peristaltic tapered channel. Thermal energy and temperature gradients cause nanoparticles to migrate randomly, affecting flow efficiency and irreversibility. Sometimes the Infected veins generate complex peristaltic waves on its walls. The mathematical model that characterizes the motion of Jeffrey magnetohydrodynamic Buongiorno's nanofluid inside a complex tapered peristaltic channel, considering the effects of electroosmotic forces is discussed. The long wavelength and low Reynolds numbers approximation is considered. The approximate solution of the nonlinear system of partial differential formulas is obtained using the Adomian decomposition method. Also, the irreversibility of the system and entropy generation are being studied. Flow characteristics with biophysical and thermal parameters are plotted and discussed. The improvement in the interstitial distances between the molecules that make up the nanofluid, which in turn works to enhance the Bejan numbers. So, one important result is by growing in both Brownian motion and thermophoresis, the Bejan numbers rise clearly. Both the Jeffrey parameter and Debye–Huckel parameter work to upsurge the loss of kinetic energy within the molecules, which reduces the temperatures inside the nanofluid and thus reduces the entropy rate, in contrast to the rest of the parameters that raise the kinetic energy inside the molecules that make up the nanofluid.

PIV study on characteristics of pedestrian-level fluctuating wind speeds around square buildings with different heights

Flow fields around four square-section buildings with different heights in boundary layer flow (BLF) were captured by PIV tests to investigate the influence of an increase in building height on fluctuating wind speed fields and pedestrian-level peak wind speed around buildings. Flow visualization results indicate that upstream stagnation levels significantly increase with increasing building height, along with higher wind speeds in approaching BLF, causing stronger front downwash flows and upwash flows behind higher buildings. Variation in flow structures with building height significantly change pedestrian-level wind speed fields, including (1) causing a significant increase in mean wind speed on the sides of buildings, although their influence on turbulent kinetic energies (TKE) in the region is not obvious; (2) causing an increase in mean wind speeds and especially TKE downstream of buildings; Accordingly, high peak pedestrian-level winds for higher buildings occur not only in windy regions beside buildings but also in generally considered low-speed wake regions. This suggests that measurement of only mean pedestrian-level wind around buildings, especially super high-rise buildings, may not be adequate and might underestimate the influence of pedestrian-level winds on pedestrians. In addition, by zoning according to different fluctuating wind characteristics around buildings, peak pedestrian-level wind speed can be estimated by gust factor with better accuracy. Meanwhile, the influence of building height can be easily reflected by constant coefficients.

Evolution of amplitude and longitude phase of tachocline Rossby waves diffusing to the photosphere

ABSTRACT Physics of magnetohydrodynamic (MHD) Rossby waves in the tachocline-layer were studied by Dikpati et al., using a fluid-particle-trajectory approach along with solving vorticity and induction equations. By extending that model to include a hydrodynamic turbulent convection zone (CZ), we examine how MHD Rossby waves generated in the tachocline might diffuse upward through the CZ to solar surface. We find that pure hydrodynamic Rossby wave amplitudes decline with height due to viscous diffusion at a rate that is independent of viscosity and increases with longitude wavenumber. Fast MHD Rossby waves amplitude declines faster with height for increasing toroidal field, due to their longitude-phase shifting with height, which increases dissipation of kinetic energy in the wave velocities. Slow MHD Rossby waves decline even faster with height because their longitude-phase shifts more rapidly with height, due to their slow phase speed. We conclude that low wavenumber HD and fast MHD Rossby waves, originating in the tachocline, might be detected at the photosphere, but slow MHD Rossby waves should be virtually impossible to detect. We infer from fluid particle trajectories that wave amplitudes declining with height and longitude phase shifting with height associated with decline, implies a powerful mechanism for tangling of magnetic fields, distinct from convective turbulence effects. This could cause a sustained or dissipative local dynamo action triggered by Rossby waves.

Soil surface roughness impacts erosion behavior through selective regulation of flow properties in rainfall-seepage scenarios

Soil surface roughness (SSR) impacts runoff dynamics of surface-subsurface and the magnitude of soil erosion, limited attention has been paid to how SSR governs runoff hydrodynamics to affect erosion behavior and the effectiveness of erosion reduction under rainfall-seepage scenarios on low-permeability purple soil slopes. Herein the seepage rates of 2, 4, and 8 L min⁻¹ were sequentially simulated under a rainfall intensity of 1.0 mm min⁻¹ among different microrelief treatments (CT: conventional tillage; AD: artificial digging; RT: ridge tillage) on purple soil slopes with gradients of 5°, 10°, and 15°. These simulations aimed to investigate the mechanisms underlying the erosion reduction benefits associated with flow properties due to microrelief. The results showed that increased SSR altered erosion kinetic energy under rainfall-seepage conditions. The benefits of rough slopes to control erosion decreased as rainfall-seepage intensity and slope gradient increased. During rainfall-seepage events, the variation in runoff behavior was regulated positively by the effect of SSR on unit stream power. However, the increasing net output power of runoff due to flow turbulence altered sediment output, thereby affecting sediment control benefits. Overall, the impact of rainfall-seepage intensity on surface roughness became more significant with increasing slope gradient. Our findings suggest the capable of integrating for interrelated microrelief and runoff processes in factors analysis of driving soil erosion at rainfall-seepage hydrologic states to elucidate erosion effect.

Ballistic characteristics of ceramic core sandwich structures

The ceramic core sandwich structure (CCSS) is a lightweight material with advantages of high anti-ballistic impact performance, high energy absorption and high specific strength. The ballistic performances of the CCSS with metal face plates hit vertically by projectiles with the nose shapes of conical, flat, and hemispherical are studied analytically and numerically in this paper. Based on the principle of energy conservation, an analytical model of ballistic characteristics of the sandwich ceramic core structure is developed. Numerical calculations are conducted, and the numerical model has been verified by experimental results from references by others. In addition, the analytical results agree well with finite element results. The effects of shape of projectile head, the thickness ratio of three plates of CCSS, and the ratio of shear strength of ceramic core to yield strength of metal face plates on the ballistic characteristics of the CCSS are discussed. It is shown that the conical-nosed projectile achieved the highest ballistic limit velocity (BLV) and the sharper nose increases the normal stress at the impact area thereby enhancing the BLV. The thickness of the ceramic core significantly influences the resistance of the CCSS and the thicker ceramic core enhances the ability of CCSS to absorb kinetic energy from the projectile. Furthermore, an appropriate increase in the yield strength of face plates can enhance the anti-ballistic impact performance of the CCSS. These insights have practical implications for the design of protective systems in military and civilian applications, where optimizing materials for impact resistance is crucial.

Atom-Vacancy-Defect-Derived Electric Hysteresis Loops and Stochastic Low-Frequency Noises in Few-Atom Layer MoS2.

Atom-vacancy-defects present in various materials yield numerous interesting physical phenomena, even obstructing high performance in some cases. On the other hand, their valuable applications to novel devices, such as nitrogen vacancy centers in diamond for quantum bits, have gathered significant attention. In particular, these tendencies become more substantial in two-dimensional (2D) (atomically) thin van der Waals layers. However, correlations with various kinds of atom defects are still under exploration. Herein, we find the stochastic behaviors of large hysteresis loops with strong photoresponse in the static electrical properties in few-atom layer semiconductors, molybdenum disulfide (MoS2). The temperature dependence and transmission electron microscopy reveal that they arise from pairs of two neighboring in-plane S-vacancy defects, which predominantly present only around the interface at the MoS2 flake/substrate, with activation energies ∼0.35 eV. The low-frequency (f) (LF) noise measurements clarify a high f shift in the two 1/f2-dependent regimes, implying stochastic behaviors of electric charges through the S-vacancy pairs with high-speed charge(spin) transitions across low kinetic energy barriers between narrow discrete states. The shallow energy sates are formed from the highly uniform S-vacancy pairs interacting with Mo atoms, which act like quantum dots. The observed stochastic operation holds promise for various application, particularly for probabilistic neuromorphic computation in artificial intelligence.

Submesoscales are a significant turbulence source in global ocean surface boundary layer

The turbulent ocean surface boundary layer is a key part of the climate system affecting both the energy and carbon cycles. Accurately simulating the boundary layer is critical in improving climate model performance, which deeply relies on our understanding of the turbulence in the boundary layer. Turbulent energy sources in the boundary layer are traditionally believed to be dominated by waves, winds and convection. Recently, submesoscale phenomena with spatial scales of 0.1~10 km at ocean fronts have been shown to also make a contribution. Here, by applying a non-dimensional turbulent kinetic energy budget equation, we show that the submesoscale geostrophic shear production at fronts is a significant turbulent energy source within the ocean boundary layer away from the sea surface. The contribution reaches 34% of the total dissipation in winter and 17% in summer at the mid-depth of the boundary layer, despite its intermittency in space and time. This work indicates fundamental deficiencies in previous conceptions of ocean boundary layer turbulence, and invites a reappraisal of the sampling scale in observations, model resolution and parameterizations, and other consequences of the global energy budget.

Energy evolution of a droplet impacting a nonuniform chemically patterned fuel cell surface

A three-dimensional nonorthogonal lattice Boltzmann model is employed to simulate a single droplet impacting a nonuniform wettable surface at the bottom of a proton exchange membrane fuel cell. The effects of nonuniform surface wettability differences in the flow channel, the impact Weber number, and the central stripe width on the energy evolution during the spreading stage are investigated. Qualitative and quantitative comparisons between the numerical simulations and experimental results indicate that the main energy loss during the initial spreading stage is attributable to momentum redistribution, while viscous dissipation is caused by shear stress and vorticity in the rim. A larger wettability difference leads to a higher net unbalanced Young’s force, resulting in stronger shear and viscous dissipation near the wettability contrast line. For smaller Weber numbers, in the early impact stage, the main loss of kinetic energy is caused by the redistribution of momentum; in the later spreading stage, the increase in surface energy is the main sink of kinetic energy. The unbalanced Young’s force hinders the spreading of the droplet at larger stripe widths, leading to a larger vortex intensity within the rim.

Vapor kinetic energy for the detection and understanding of atmospheric rivers

Poleward water vapor transport in the midlatitudes mainly occurs in meandering filaments of intense water vapor transport, spanning thousands of kilometers long and hundreds of kilometers wide and moving eastward. The water vapor filaments are known as atmospheric rivers (ARs). They can cause extreme wind gusts, intense precipitation, and flooding along densely populated coastal regions. Many recent studies about ARs focused on the statistical analyses of ARs, but a process-level understanding of ARs remains elusive. Here we show that ARs are streams of air with enhanced vapor kinetic energy (VKE) and derive a governing equation for Integrated VKE to understand what contributes to the evolution of ARs. We find that ARs grow mainly because of potential energy conversion to kinetic energy, decay largely owing to condensation and turbulence, and the eastward movement is primarily due to horizontal advection of VKE. Our VKE framework complements the integrated vapor transport framework, which is popular for identifying ARs but lacks a prognostic equation for understanding the physical processes.

Trade-Off Between Growth Regimes in Chlorella vulgaris: Impact on Carotenoid Production

With the increasing awareness of socio-environmental issues, a global trend has emerged emphasizing the valorization of natural ingredients that promote health and well-being within sustainable production systems, such as microalgae-based carotenoids. Currently, little is understood about the correlation between biomass productivity and carotenoid content, which is a fundamental parameter for facilitating the immediate expansion of microalgae bioprocesses and ensuring the availability and industrial viability of these compounds. In this context, this study aims to investigate the carotenoid profile of Chlorella vulgaris through growth curve experiments conducted under photoautotrophic and heterotrophic regimes. Additionally, a trade-off analysis was performed for the production of carotenoids from microalgae. Carotenoids were quantified using high-performance liquid chromatography coupled with diode array and mass spectrometry detectors (HPLC-PDA-MS/MS). The performance of kinetic phases and energy demands across growth regimes was assessed to provide insights into production trade-offs. The results indicated that a total of 22 different carotenoids were identified in all the extracts. The all-trans-lutein and all-trans-β-carotene were the majority compounds. The total carotenoid content of Chlorella vulgaris revealed significant differences in the kinetic phases of carotenoid production, indicating that carotenoid volumetric production is only viable if the cultures are conducted until the log and stationary phases, based on the function of the biomass volumetric production (weight.volume−1). Therefore, the best trade-off for the process was to provide photoautotrophic growth until the exponential phase (log). Under this condition, the maximum carotenoid and lutein content was 2921.70 µg.L−1, reaching a maximum cell biomass of 1.46 g.L−1. From an environmental/economic point of view, the energy demand was 7.74 kWh.L−1. Finally, the scientific advances achieved in this study provide a holistic view of the influence of the main cultivation methods on the production of microalgae carotenoids, suggesting a viable initial direction for different industrial applications.

The generalized quasilinear approximation of two-dimensional Rayleigh–Bénard convection

In the generalized quasilinear approximation (GQLA) (Marston et al., Phys. Rev. Lett., vol. 116, 2016, 214501), a threshold wavenumber ( $k_0$ ) in the direction of translational symmetry segregates the total into large- ( $l$ ) and small-scale ( $h$ ) fields. While the governing equation for the large-scale field is fully nonlinear, that for the small scales is linearized with respect to the large-scale field. In addition, some nonlinear triad interactions are omitted in the GQLA. Herein, the GQLA is applied to two-dimensional planar Rayleigh–Bénard convection (RBC). A scale separation between the large-scale convection rolls and small-scale turbulent fluctuations is typical in RBC. The present work explores the efficacy of GQLA in capturing the scale-by-scale energy transfer processes in RBC. The initial condition for the GQLA simulations was either the statistically stationary state obtained in direct numerical simulation (DNS) or random fluctuations superimposed on the linear conductive temperature profile and $\boldsymbol {u}=0$ . The GQLA simulations can capture the convection rolls for $k_0$ larger than or equal to the dominant wavenumber for thermal driving of the flow ( $k_0 \ge k_{\hat {Q}}$ ). Additionally, the GQLA emulates the fully nonlinear dynamics for $k_0$ larger than or equal to the first harmonic of the convection-roll wavenumber ( $k_0 \ge 2k_{roll}$ ). In the intermediate regime with $2k_{roll} > k_0 \ge k_{\hat {Q}}$ , the dynamics captured in GQLA simulations is different from the DNS. In DNS, two primary energy transfer processes dominate: (i) the energy transfer to/from the convection rolls and (ii) the scale-by-scale inverse kinetic energy and forward thermal energy cascades mediated by the convection rolls. The fully nonlinear dynamics is emulated by GQLA when these energy transfer processes are faithfully reproduced. Utilizing the framework of altering the triad interactions in GQLA, an additional intrusive calculation, including target triad interactions, is performed here to study their influence. This intrusive calculation shows that the convection rolls are not captured in GQLA for $k_0 < k_{\hat {Q}}$ because of the exclusion of the $h \to l \to l$ and $l \to h \to h$ triad interactions in GQLA. The inclusion of these triad interactions in the intrusive calculation yields the convection rolls, and the reproduced dynamics is similar to that of the intermediate GQLA regime with $2k_{roll} > k_0 \ge k_{\hat {Q}}$ .

Interactions between swell and colinear wind short crested waves, following and opposing

When wind blows over a water surface during a swell, it generates short-crested, three-dimensional waves that interact with the underlying flow field through a mechanism that ultimately increases the average energy. In the present work, two test cases in which wind is flowing following and opposing a swell are analysed with experiments and are compared with wind–waves-only and swell-only cases. The analysis of the free surface fluctuation and of the flow field, with the three components of fluid velocity measured at the same time through a stereo particle image velocimetry system, leads to an accurate quantification of the energy distribution, of the structure of the oscillating, fluctuating (due to wind–waves) and turbulent kinetic energy, without assumptions on the structure of the flow. The findings demonstrate that the transverse dynamics is a pivotal factor in the transfer of energy in the near-free surface domain, and elucidate the energy transfer between wind–waves and swell. The results also confirm the reduction of oscillating kinetic energy of the swell in the presence of short wind–waves, a process interpreted with different possible mechanisms. There is evidence of the enhancement of wind action in the presence of swell compared to that in the case of wind–waves-only, confirming that energy transfer from the wind to the sea is enhanced when wind flows over a swell. Consequently, when the fetch is influenced by swells generated or propagated from different regions, and during multi-peak sea storms, wave generation models should account for this amplification.

The Aerodynamic Assessment and Shot Point Position Accuracy of UAV Seismic Source

An unmanned aerial vehicle (UAV) seismic source, suitable for complex terrains due to its eco-friendly, cost-effective, and efficient nature, operates by hovering and releasing impact objects to generate seismic waves. The aerodynamic behavior of these impact objects is vital for shotpoint position accuracy and drag magnitude. Excessive drag will result in the loss of seismic source energy, whereas the deviations of the shotpoint position will disrupt the geometric structure of the observation system, significantly impacting the quality of seismic data acquisition. Through theoretical calculations, the influencing factors of air resistance and cross-wind deflection are analyzed. Air resistance increases with the increase in mass, cross-sectional area, speed, and drag coefficient. Increasing the mass and throwing height can increase the upper limit of the output, but after the air resistance and gravity are balanced, the output kinetic energy of the drone’s seismic source will no longer increase when the throwing height is increased. Using computational fluid dynamics simulations and field tests, this study examines the aerodynamics of four prevalent impact object designs. The results show that shuttle and spherical structures have the least drag during descent and are less influenced by crosswinds, thus being optimal for this application. Field measurement data are also presented for reference.

Experimental study on the aerodynamic characteristics and wake flow feature of triangular prisms with various round corner radius

In this work, particle image velocimetry (PIV) and wind pressure measurements are employed in the wind tunnel to investigate triangular prisms with different rounded corner radius. The effect of rounded corner radius on wind pressure distribution, aerodynamic force, and wake flow characteristics are analyzed. Results indicate that the surface wind pressure can be effectively reduced through filleting treatment, with an average drag coefficient decrease of 52.7% as the corner shape transitions from sharp to round. The continuous increase of the radius of the rounded corner causes an accretion of the fluctuating lift coefficient, and a slow decrease of the drag coefficient. The modification of the corner radius has a limited impact on the vortex shedding frequency, but the shedding vortex tend to gather the leeward side. Additionally, statistical analysis of wake flow shows that an increment in the rounded corner radius leads to a significant reduction in the wake recirculation region, amounting to 20.16%. Concurrently, the peak values of turbulent kinetic energy and Reynolds stress exhibit a pattern of initial increase followed by a decrease. On the other hand, results of proper orthogonal decomposition suggest that the spatial distribution of vortex structures becomes increasingly compact with the enlargement of the rounded corner radius.