Entry Velocity Research Articles

Numerical Investigation of Geometrical Design Effect on the Submerged Inlet Aerodynamics Characteristics

In the present study, turbulent flow at submerged inlets is numerically studied. Five different geometries including the standard inlet developed by National Advisory Committee for Aeronautics (NACA), divergent inlet, parallel inlet and two new proposed geometries are compared. The effects of the boundary layer thickness ratio (0.31, 0.8 and 2.56) defined as the ratio between the boundary layer thickness (\( \delta \)) and the entrance depth (d) and velocity ratio defined as the ratio between the flow velocity at the duct entrance and the free stream (0.2–1.6) on their performance are further investigated. Moreover, the \( \,K - \omega \; \) model is used to simulate the three-dimensional, incompressible and turbulent flow of interest. NACA inlet is validated with experimental data. Results showed that in all studied cases, increasing the boundary layer thickness has a negative effect on the Ram recovery ratio (or efficiency); however, the effect of the velocity ratio on the Ram recovery ratio was different with an initial increase followed by a decrease in the efficiency. It is shown that our two proposed inlets present the same efficiency as the NACA inlet, while the efficiency for the divergent and parallel inlets was lower. Interestingly, the proposed inlets show a lower drag force compared to the NACA inlet at the high velocity ratios.

Comparing analytical and numerical approaches to meteoroid orbit determination using Hayabusa telemetry

AbstractFireball networks establish the trajectories of meteoritic material passing through Earth's atmosphere, from which they can derive pre‐entry orbits. Triangulated atmospheric trajectory data require different orbit determination methods to those applied to observational data beyond the Earth's sphere of influence, such as telescopic observations of asteroids. Currently, the vast majority of fireball networks determine and publish orbital data using an analytical approach, with little flexibility to include orbital perturbations. Here, we present a novel numerical technique for determining meteoroid orbits from fireball network data and compare it to previously established methods. The re‐entry of the Hayabusa spacecraft, with its known pre‐Earth orbit, provides a unique opportunity to perform this comparison as it was observed by fireball network cameras. As initial sightings of the Hayabusa spacecraft and capsule were made at different altitudes, we are able to quantify the atmosphere's influence on the determined pre‐Earth orbit. Considering these trajectories independently, we found the orbits determined by the novel numerical approach to align closer to JAXA's telemetry in both cases. Using simulations, we determine the atmospheric perturbation to become significant at ~90 km—higher than the first observations of typical meteorite dropping events. Using further simulations, we find the most substantial differences between techniques to occur at both low entry velocities and Moon passing trajectories. These regions of comparative divergence demonstrate the need for perturbation inclusion within the chosen orbit determination algorithm.

Effects of multi inlet guide channels on the performance of a cyclone separator

Widely usage of cyclone separator, especially in industries, makes it not only one of the most interesting subject of papers nowadays, but research and development of it should follow necessarily. The unusual design of this cyclone makes it more useful and functional. This design causes to form a strong vortex flow in the cyclone, which increases the centrifugal force acting on each particle separately, increases the collection efficiency as well as decrease the cut-off diameter. So, simulation of the turbulent 3D flow has been done with the finite volume method and RSM turbulence model. The major contribution of the total cyclone pressure drop has occurred in the upper section of cyclone and guide channels, which increase the entered velocity to the main body of the cyclone. The results represent a uniform distribution of static pressure patterns at cyclone heights for each velocity as well as a uniform flow field pattern in the cyclone. In comparison with usual cyclones, because of the special design of inlet guide channels, not only the entrance velocity of flow to the main cyclone body has been increased, but the inappropriate moving of flow after the entrance to the main body toward the cyclone's top section doesn't occur. The cut-off diameter reduced by 0.2 μm in comparison with the usual cyclone separator. With 20% increasing in the inlet velocity, the maximum static pressure in all sections increases by approximately 41%, while the 20% reduction in the inlet velocity, reduces the maximum static pressure in all sections by 55% to 58%. A 20% increase in velocity compared to the initial velocity of 8.809 m/s, reducing the cut-off diameter to approximately 0.6 μm. A 20% decrease in inlet velocity, the separation efficiency is reduced in general and increases the cut-off diameter to 0.9 μm. The Stokes number smaller than 1, should be expressed as an appropriate criterion to select between two main aspects of Eulerian-Lagrangian and Eulerian- Eulerian approach. Reducing the inlet velocity amplifies the assumption of the Eulerian-Lagrangian aspect instead of the Eulerian- Eulerian approach. About the Euler number, the 20% increasing the inlet velocity has increased the pressure drop in the cyclone, but the inlet velocity seems to be more effective on the flow kinetic energy rather than an influence on the pressure drop.

Cosmic dust fluxes in the atmospheres of Earth, Mars, and Venus

The ablation of cosmic dust injects a range of metals into planetary upper atmospheres. In addition, dust particles which survive atmospheric entry can be an important source of organic material at a planetary surface. In this study the contribution of metals and organics from three cosmic dust sources – Jupiter-Family comets (JFCs), the Asteroid belt (AST), and Halley-Type comets (HTCs) – to the atmospheres of Earth, Mars and Venus is estimated by combining a Chemical Ablation Model (CABMOD) with a Zodiacal Cloud Model (ZoDy). ZoDy provides the mass, velocity, and radiant distributions for JFC, AST, and HTC particles. JFCs are shown to be the main mass contributor in all three atmospheres (68% for Venus, 70% Earth, and 52% for Mars), providing a total input mass for Venus, Earth and Mars of 31 ± 18 t d−1, 28 ± 16 t d−1 and 2 ± 1 t d−1, respectively. The mass contribution of AST particles increases with heliocentric distance (6% for Venus, 9% for Earth, and 14% for Mars). A novel multiphase treatment in CABMOD, tested experimentally in a Meteoric Ablation Simulator, is implemented to quantify atmospheric ablation from both the silicate melt and Fe-Ni metal domains. The ratio of Fe:Ni ablation fluxes at Earth, Mars and Venus are predicted to be close to their CI chondritic ratio of 18, in agreement with mass spectrometric measurements of Fe+:Ni+ = 20−8+13 in the terrestrial ionosphere. In contrast, lidar measurements of the neutral atoms at Earth indicate Fe:Ni = 38 ± 11, and observations by the Neutral Gas and Ion Mass Spectrometer on the MAVEN spacecraft at Mars indicate Fe+:Ni+ = 43−10+13. Given the slower average entry velocity of cosmic dust particles at Mars, the accretion rate of unmelted particles in Mars represents 60% of the total input mass, of which a significant fraction of the total unmelted mass (22%) does not reach an organic pyrolysis temperature (~900 K), leading to a flux of intact carbon of 14 kg d−1. This is significantly smaller than previous estimates.

Numerical study on bubble-liquid two-phase turbulent hydrodynamics in extremely narrow shape bioreactor

The main objective of this work was to determine the influence of the bubble-liquid two-phase turbulent hydrodynamics on cell culture in extremely narrow shape bioreactor. An improved second-order moment bubble-liquid turbulent model and built in-house calculation source code were developed to numerically simulate the hydrodynamics that related to cell damage. Two higher gas entrance velocities of 78.3 m/s and 104.4 m/s were employed and their effects on hydrodynamic parameters, such as bubble rising and liquid flow velocities, bubble normal and shear stresses, correlation of bubble-liquid normal stresses, turbulent kinetic energy and turbulent energy dissipation rate of bubble and liquid were investigated details. All increased with gas entrance velocities increase but failed to explain an experimental observation that higher cell death at jetting region. A new correlation definition, bubble-liquid two-phase turbulent energy production term was proposed to successfully elaborate it, as well as the effects of high gas entrance velocities. Simulation results showed turbulent energy production terms are the largest at near gas jetting regions in comparison to those of developed flow regions, which are in good agreements with experimental result. Furthermore, extremely narrow shape deteriorated the cell living environment.

Numerical investigations on the oblique water entry of high-speed projectiles

In this paper, we investigate the main characteristics of oblique water entry of high-speed cylindrical projectiles, which involves multiphase flows due to cavitation. Numerical simulations are performed by solving Reynolds-averaged Navier–Stokes (RANS) equations coupled with 6-degree of freedom (DOF) rigid-body motion equations. The model is validated firstly by comparing with previous results. Then the studies of different entry conditions are performed, and we find that the velocity attenuation during the entry process is mainly affected by the projectile geometric parameters such as its head shape and length, rather than the entry angles and velocities. The drag coefficient is also dominated by the head shape. Furthermore, the time of surface closure of cavity is linear with the entry velocity of the projectile.

Full-scale numerical study on the flow characteristics and mal-distribution phenomena in SG steam-water separation system of an advanced PWR

The steam-water separation system is of great importance to ensuring the steam quality in a PWR UTSG. In the present work, the full-scale three-dimensional CFD analysis is performed to study the mal-distribution steam flow in the system using ANSYS-FLUENT platform. A full-scale model of newly-designed PWR is established and all the sophisticated structures of 19 swirl-vane separators are modeled. Besides, the porous medium model is adopted to simplify the steam flow inside the dryers because of the complex structure of wave-type vanes. Employing CFD methodologies, detailed flow characteristics in the whole system are captured, especially the velocity fields of steam at inlets of 7 dryer units. The outcomes show that the maximum unit-area mass-flow rate appears at the entrance of #4 dryer which is in the central part of dryers. In addition, the maximum entry velocity is 2.136 m/s, while the velocity is decreased to 1.049 m/s, lower than the critical velocity, with the application of an orifice plate assembly with the perforation in different calibers on the plate. Also, the effect of the separator down-comer on the mal-distribution phenomenon is also analyzed. In general, the current work could be expected to be a basis for the future optimization on moisture separation components in the steam generator.

Maximum acceleration performance of professional soccer players in linear sprints: Is there a direct connection with change-of-direction ability?

The purpose of this study was to examine the selective influences of the maximum acceleration capability on change of direction (COD) speed, COD deficit, linear sprint speed, sprint momentum, and loaded and unloaded vertical jump performances in forty-nine male professional soccer players (24.3 ± 4.2 years; 75.4 ± 5.4 kg; 177.9 ± 6.4 cm). Soccer players performed the assessments in the following order: 1) squat and countermovement jumps; 2) 20-m sprinting speed test; 3) Zigzag COD ability test; and 4) bar-power outputs in the jump squat exercise. Athletes were divided, using a median split analysis, into two different groups according to their maximum acceleration rates from zero to 5-m (e.g., higher and lower ACC 0-5-m). Magnitude-based inference was used to compare the differences in the physical test results between “higher” and “lower” acceleration groups. A selective influence of the maximum acceleration ability on speed-power tests was observed, as the higher acceleration group demonstrated likely to almost certain higher performances than the lower acceleration group in all measurements (effect sizes varying from 0.66 [for sprint momentum in 20-m] to 2.39 [for sprint velocity in 5-m]). Conversely, the higher acceleration group demonstrated a higher COD deficit when compared to the lower acceleration group (ES = 0.55). This indicates compromised efficiency to perform COD maneuvers in this group of players. In summary, it was observed that soccer players with higher maximum acceleration rates are equally able to jump higher, sprint faster (over short distances), and achieve higher COD velocities than their slower counterparts. However, they appear to be less efficient at changing direction, which may be related to their reduced ability to deal with greater entry and exit velocities, or counterbalance the associated mechanical consequences (i.e., greater inertia) of being faster and more powerful.

Design and load reduction performance analysis of mitigator of AUV during high speed water entry

The Autonomous Underwater Vehicle (AUV) will suffer severe impact load during the water entry, and its shell structure will undergo elastoplastic deformation, even breakage or damage, which seriously threatens the safety and reliability of the AUV. Therefore, it is necessary to carry out research on the buffering technology of the impact load of the vehicle into the water to ensure that the AUV can enter the water safely and reliably. In this paper, a mitigator is designed to reduce the impact load of the AUV entering the water. Numerical simulations based on the explicit finite element method with an Arbitrary-Lagrangian Eulerian (ALE) solver are carried out to study the mitigation characteristic of the designed mitigator. The accuracy of the model was verified by the experimental results of the water-entry of the small sphere, and the mesh independence was verified to determine the mesh size. Then, the effects of initial conditions such as buffer length, buffer material density, entry velocity and entry angle on the cushioning effect of the buffer head cap were studied. When the vertical water entry velocity is 50 m/s, the impact load reduction ratio is 42.2%; while the water entry angle is 60° and the water entry velocity is 50 m/s, the axial load reduction ratio is 28.8%, and the normal load reduction ratio is 27.8%. These conclusions will be useful for the designing of the crashworthy structural and the analysis of underwater weapon impact.

Analytical Solution of Water Vapor Condensation in Flow Channel of Battery Pack

The analytical solutions for condensation (and evaporation) rates of laminar humid air flow in the channels of a battery pack at both entrance and downstream regions are obtained/modeled. The effects of the entrance fluid velocity profile and the aspect ratio of the flow channel are taken into consideration. Initially, an analytical solution for laminar humid air flows' condensation at the flow channel with infinite aspect ratio and fully developed flow profile at the entrance is obtained. The solution is in good agreement with the simulation result obtained from a correlated fluent condensation model. After performing simulations of water vapor condensation and evaporation in the flow channel for different aspect ratios and entrance velocity profiles, the analytical solutions of condensation and evaporation rate of water vapor are presented in analytic forms by adding appropriate coefficients/correction factors to the solution for the flow in the channel with infinite aspect ratio. The resulting model accurately captures the effects of the entrance velocity profile and aspect ratio.

Rheotaxis and swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and application to design of fishway entrances

The objective of this research was to determine the effects of diel cycle and flow velocity on rheotaxis, measure the swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and use the results to recommend an appropriate fishway entrance velocity and fish lift operating schedule. PIT tagging was used to monitor fish rheotaxis for 48 h in four channels with differing flow characteristics. Swimming performance tests were conducted in a swimming respirometer and induced flow speed, critical swimming speed and critical burst speed were determined. The relationship between flow velocity and fish swimming behavior was analyzed to determine the optimal attraction flow velocity. There were three primary findings. (1) Test fish were active both day and night, but made more attempts, had longer retention times, and swam longer through-water distances in all channels during the day. (2) Entry, retention, and effort were maximum at a flow velocity of 0.2 m/s (26% of absolute critical swimming speed (m/s) and 29% of relative critical swimming speed (bl/s)). (3) Attempt number, retention time and through-water distance increased with body length in the channel with greatest activity. Collectively, these data suggest that passage of P. pingi will be optimized by fishways operating throughout the day and most of the night, although these conditions could lead to size-based selectivity in passage.

Sheath formation in collisional, low pressure, and magnetized plasma

Formation of a plasma sheath is studied in collisional and magnetized low pressure plasma. The magnetic field has a tilted configuration. The model provides plasma profiles for a wide range of magnetic field strengths and tilting angles. It is shown that the sheath entry velocity in the magnetized case should be chosen for all three components of ion velocity rather than a single component (which is directed along the sheath). It is found in the collisionless case that the net magnitude of the ion velocity gains the characteristic ion speed (Bohm speed). This, in turn, is found to retain the monotonic variation of the ion density. Ionization is considered with constant ionizing frequency. Comments are made on the sheath thickness and the retention of the Debye sheath at a low angle, for low pressure magnetized plasma.

Experimental study on water entry of cylindrical projectiles with different nose shapes

Water entry experiments of projectiles with different nose shapes were performed under different entry angles and velocities using high-speed photography technology. The cavity flow characteristics of the near water surface, including splash jet, splash crown, surface seal of cavity, pull away, deep seal of cavity and cavity collapses, were systematically investigated using a high-speed camera. The emphasis of the study is paid on the effect of nose shape, water entry angle and velocity on the evolution of the air entraining cavity. The experimental results demonstrate that the nose shape of projectile has a significant influence on the jet flow, the cavity diameter and trajectory stability in the case of certain other conditions. On the other hand, the splash scale, cavity diameter increase gradually with the increasing of the water entry velocity, as well as the cavitation closed in advance. Furthermore, the water entry angle of the projectile plays an important role in the cavity evolution and the close type.

Sampling rate effect on wedge pressure record in water entry by experiment

Water entry experiment is the most reliable method by which impact pressures on marine structures are measured. Several parameters have to be controlled during the water entry experiments to obtain accurate and reliable results. Sampling rate of data acquisition system is one of the influencing factors. In this paper, the effect of sampling rate on impact pressure on wedge water entry experiments is investigated. A wide range of wedges with deadrise angles of 5°–35° are dropped into water at the entry velocity of 3.13 m/s and impact pressures are recorded with different sampling rates. Results are compared to analyze the effect of sampling rate on outcomes. Finally, to mitigate the negative aspects, some thresholds of sampling rate are determined for different wedges. It was found that for wedges with deadrise angles of 25° and higher, a sampling rate of 25 kHz is adequate for this configuration. This sampling rate; however, is not appropriate for deadrise angles lower than 20° where a higher rate is needed. Results indicate that the acceptable sampling rate for a wedge of 5° deadrise angle is 600 kHz at water entry velocity of 3.13 m/s.

Numerical Simulation of Heat Transfer Performance between Molten Salt and Supercritical CO2 in Double-pipe Heat Exchanger

As a tranditional heat exchanger, double-pipe heat exchanger can bring a better heat transfer performance when using supercritical carbon dioxide (S-CO2) and molten salt as a working fluid. In this study, the effects of structure ratio of the heat exchanger and the entrance velocity of S-CO2 on heat transfer and flow resistance are investigated numerically. The results show that the velocity of S-CO2 plays a major role in a small flow channel determining the overall performance. It concludes that reducing the flow resistance and improve the performance of heat transfer needs to be considered first in the optimal design of a double-pipe heat exchanger using S-CO2 as working fluid.

Selection of filter parameters of Individual water supply systems

The paper is devoted to the problem of optimal design, construction and operation of water supply systems and their elements. The key element of the system is a water well. The quality of its design and construction determines the operation of the water intake as a whole. Disadvantages in the construction of a well lead to disruption of the entire water supply system of a particular object. The paper proposed a methodology for selecting the optimal diameter and length of the well filter of a water well. Based on the methodology, an example of filter parameters selection for hydrogeological conditions of the city of Kursk is given. The above calculation showed that the use of the entrance velocity criterion in the design of wells can significantly reduce the cost of well construction while ensuring the design flow rate and allowable lowering of the water level. The cost of the filter, depending on the well design, is 20-30% of the total price for its construction. The most important filter parameters affecting the cost of a well are its length and diameter. Justifying the minimum diameter of the filter that ensures the designed water intake and allowable dewatering can significantly reduce the cost of the well, taking into account the fact that modern pumping equipment allows the use of columns of small diameter above the filter.

Flow Analysis through Collector Well Laterals: A Case Study from Sonoma County Water Agency, California

The Sonoma County Water Agency (SWCA) uses six radial collector wells along the Russian River west of Santa Rosa, to provide water for several municipalities and water districts in north-western California. Three collector wells (1, 2, and 6) are located in the Wohler area, and three collector wells (3, 4, and 5) are located in the Mirabel area. The objective of this paper is to highlight the performance of the three collector wells located in the Mirabel area since their construction. The 2015 investigation showed a lower performance of Collectors 3 and 4 compared to their original performances after construction in 1975, while the performance of Collector 5 was relatively stable since 1982. The potential change in capacity could be due to the increase in encrustation observed during the visual inspection of laterals in all three collector wells. Overall, the three collectors are still within the optimal design parameters (screen entrance velocity < 0.305 m min−1 and axial flow velocity of lateral screens < 1.524 m s−1).

Simulating Gas Giant Atmospheric Entry Using Helium and Neon Test Gas Substitutions

Flight into the gas giant planets involves atmospheric entry velocities between 20 and , which are mostly beyond the capabilities of current ground testing facilities that make use of test models. Using an expansion tube, this paper investigates how increasing the percentage of helium in the test gas, or substituting the helium for the heavier noble gas neon, can be used to generate representative shock-layer conditions associated with Uranus and Saturn entry. Theoretically, it was found that either test gas substitution should make it possible to simulate Uranus or Saturn entry shock layers, which was confirmed experimentally for the helium substitution. Lower percentages of the substituted gas were required for neon; however, the helium substitution was found to be able to maintain the flow stagnation enthalpy in the driven sections of the facility with changing diluent fraction. Noting the current interest in sending atmospheric entry probes to both of these planets, this demonstrates that the required experimental capabilities are available for performing simulated experiments using test models.

Experimental study of cavity characteristic induced by vertical water entry impact of a projectile with a 90° cone-shaped head at different velocities

Experimental studies of the vertical water entry of projectile with 90° cone-shaped head were conducted by using high speed camera. The pinch-off types and evolutionary process of the cavity were comprehensively discussed at different water entry impact velocities. The variations of cavitation closure time, water depth at the closure point and length of the warhead cavitation with water entry velocities, as well as the cavitation diameter at different water depth positions were analyzed. The jet phenomenon caused by the closure of the water curtain and contraction-rising process of the cavity near undisturbed free surface were studied, as well as the coupled effect between them. The cavity wall fluctuation occurring after the deep seal was discussed. The results show that with the increase of water entry velocity, the quasi-static closure, shallow closure, deep closure and surface closure of the cavitation occurs respectively, and each closure mode corresponds to a velocity range; the critical water entry velocity of forming cavitation is 0.657 m/s. The diameter of the cavitation presents a nonlinear increase along with the water depth. The initial cavity expansion velocity increases, the maximum diameter of the cavity decreases, the expansion section shortens, the contraction section lengthens, and the acceleration of the expansion and contraction of the cavity increases along with the increase of the water depth at the same time. When the water curtain closes, there will be upward and downward jets, and when the downward jet velocity is relatively large, the projectile motion will be affected. The strength of a water jet induced by longitudinal upward contraction of the cavity near free surface is proportional to the volume of cavity and pinch-off depth. A large strength upward water jet is induced by the coupling of the above all water jet. The longitudinal contraction of the cavity around the projectile and the impact effect of downward jet on projectile would cause the force change of the projectile after deep seal. The fluctuation of the projectile's velocity because of its force change brings the velocity change of fluid and then leads to the fluctuation of the cavity wall. The fluctuation of cavity wall follows the principle of independent expansion of cavitation section.

Comparison of attraction, entrance and passage of downstream migrant American eels (Anguilla rostrata) through airlift and siphon deep entrance bypass systems

Downstream migrating anguillid eels face many barriers including turbines and pumps at impoundments for water abstraction, power generation and water level control, when attempting to exit the freshwater catchment to reach spawning grounds. Multiple eel species worldwide are facing different levels of endangerment and alleviating the impacts of barriers to migration is essential to allow completion of the life cycle. Deep bypass systems with entrances located near the riverbed hold some promise for increased effectiveness compared to traditional downstream guidance and bypass facilities with entrances near the surface, as eels typically occupy the bottom of the water column. Here we evaluate two deep entrance bypass designs; an airlift (the Conte Airlift) and a conventional gravity siphon of the same entrance dimensions. Tests were performed using migratory silver-phase American eels (Anguilla rostrata), at night, in a simulated forebay environment. Passage performance was monitored over a 3 h test period using both PIT (passive integrated transponder) tag and video recording equipment. Entrance velocity was fixed at 1.2 m s−1 in each of 8 test runs with cohort size fixed in six runs at 14 and in two runs at 42. Test eels readily located, entered and passed both bypass designs. Differences in performance metrics between the airlift and siphon were not statistically significant (P > 0.05) with linked mean values of 74.5%, 90.5% and 100%, respectively. Eel length did not affect passage speed (P > 0.05) or slip ratio, i.e., the measured eel velocity relative to fluid velocity. The slip ratio was, however, greater in the siphon than in the airlift (P < 0.01) within identical vertical upflow sections of the test equipment. Siphon slip ratios in the upflow vertical section were comparable to those established for the horizontal and downflow sections. Fish density did not affect attraction and passage through the airlift or siphon. No mortality or signs of injury were observed on any of the test eels through a 48 h post-test observation period. Both airlift and siphon downstream bypass systems show promise as effective technologies for protection of downstream migrating eels at a variety of water diversion or hydroelectric sites that pose threats of impingement, entrainment, and turbine mortality.