Effect Of Step Height Research Articles

Effect of Step Height and Visual Feedback on the Lower Limb Kinematics Before and After Landing

Effect of Step Height and Visual Feedback on the Lower Limb Kinematics Before and After Landing

The Fukuda stepping test is associated with various patterns of displacement

Abstract Objective: This study was to characterize individual path trajectories during the 50-step Fukuda stepping test (FST) and to determine the impact of step height on these trajectories. Methods: Kinematic data from the shoulders and feet were recorded in 12 young healthy adults while performing the FST at a comfortable step height (CoStep) and while stepping with lifting the knees high (HiStep). Path trajectories were depicted by step-by-step displacement of the right and left toes, and body rotation was obtained from the rotation of the shoulders. The effect of step height on the distance traveled and the final anteroposterior (AP) and mediolateral displacements and rotation were determined with paired t-tests. Results: Path trajectories were composed of various combinations of forward displacement, lateral deviation, and rotation to the left or right. In comparison with CoStep, the mean AP displacement and mean distance traveled were significantly shorter in HiStep (P < 0.05) while the mean rotation was significantly larger in HiStep (P < 0.05), but the displacement patterns were not modified. Conclusion: We found that the path trajectories vary greatly among participants, and that step height has a significant impact on the magnitude of displacements and rotation during the FST.

Algebraic Method for Approximate Solution of Scattering of Surface Waves by Thin Vertical Barrier Over a Stepped Bottom Topography

A study on interaction of surface water waves by thin vertical rigid barrier over a step type bottom topography is analysed. The associated mixed boundary value problem is solved using the eigenfunction expansion of the velocity potential. The resulting system of equations, avoiding the traditional approach of employing application of orthogonality relations, is solved using algebraic least squares method giving rise the numerical values of the reflection and transmission coefficients by the barrier over step. The energy balance relation for the given problem is derived and verified numerically ensuring the correctness of the present results. The present results are also compared with the data available in the literature for the validation purpose. The effect of step height, length of the barrier and angle of incidence on the reflection coefficient and the non-dimensional horizontal force on the barrier have been investigated through different plots. It is observed that barrier along with step works as an effective barrier to reflect more incident waves causing calm zone along the leeside.

Peking geckos (Gekko swinhonis) traversing upward steps: the effect of step height on the transition from horizontal to vertical locomotion.

The ability to transition between surfaces (e.g., from the ground to vertical barriers, such as walls, tree trunks, or rock surfaces) is important for the Peking gecko's (Gekko swinhonis Günther 1864) survival. However, quantitative research on gecko's kinematic performance and the effect of obstacle height during transitional locomotion remains scarce. In this study, the transitional locomotion of geckos facing different obstacle heights was assessed. Remarkably, geckos demonstrated a bimodal locomotion ability, as they could climb and jump. Climbing was more common on smaller obstacles and took longer than jumping. The jumping type depended on the obstacle height: when geckos could jump onto the obstacle, the vertical velocity increased with obstacle height; however, geckos jumped from a closer position when the obstacle height exceeded this range and would get attached to the vertical surface. A stability analysis of vertical surface landing using a collision model revealed that geckos can reduce their restraint impulse by increasing the landing angle through limb extension close to the body, consequently dissipating collision energy and reducing their horizontal and vertical velocities. The findings of this study reveal the adaptations evolved by geckos to move in their environments and may have applicability in the robotics field.

The Effects of Step Height and External Force on the Water Droplet Movement on the Wetting Gradient Surface Using Molecular Dynamics

The Effects of Step Height and External Force on the Water Droplet Movement on the Wetting Gradient Surface Using Molecular Dynamics

Augmentation of Heat Transfer and AL2O3-Nanofluid Flow Over Vertical Double Forward-Facing Step (DFFS)

Nanofluids are recommended to improve heat transfer in cooling and heating systems, resulting in significant benefits. This paper numerically investigates turbulent heat transfer and Al2O3-nanofluid flow over a vertical double forward-facing step. A two dimensional with three different cases of vertical DFFS is conducted using K-ɛ model based on finite volume method for volume fraction of nanofluids varied for 1%, 2% ,3% and Reynolds number changed from 10000 to 40000. With increasing Reynolds number, there is an increase in local coefficients of heat transfer, with the highest coefficient of heat transfer detected at Re=40000. For volume fractions of Al2O3= 3% and Reynolds numbers of 40000, the effects of step height on surface coefficients of heat transfer are described. In addition, the findings have discovered that as the volume fraction of Al2O3 nanofluids has increased, the coefficient of heat transfer has increased as well, with the maximum coefficient of heat transfer occurring at a volume fraction of Al2O3 nanofluids of 3%. Furthermore, the first step-case 2 local coefficient of heat transfer has been higher than the first step-cases 1 and 3. Increased Re number causes a sharp drop in local static pressure at the first and at the second steps. Due to the recirculation flow, there has been a reduction in velocity profile near the first and second steps, indicating an increase in heat transfer rate. Moreover, velocity counters are shown in order to demonstrate how Reynolds number affects the size of the recirculation zone. In addition, the turbulence kinetic energy counter has been shown in order to demonstrate how to achieve thermal efficiency in the second step in all the cases.

Mixing efficiency of hydrogen multijet through backward-facing steps at supersonic flow

Increasing the fuel mixing performance in the combustor of scramjet substantially improves the overall efficiency of the scramjet engine. In this article, computational fluid dynamic is used to study the impacts of hydrogen jets injection through the backward-facing multi-steps on the fuel distribution and mixing zone at the supersonic air stream of Mach = 4. This study also analyzes the jet flow feature and circulation of jets in different sections of the combustor at downstream of the multi-injectors. Reynolds average Navier-Stocks equations are solved with SST turbulence model for achieving a precise and acceptable solution. The effects of step height on the jet features are also examined. According to circulation evaluation, low jet total pressure (pressure ratio = 0.1) and high step depth (step depth = 1 mm) is the optimum condition for achieving high circulation value. Our investigations show that the mixing efficiency of the hydrogen multijets improves up to 15% when the step height increases from 0.5 mm to 1 mm.

Effects of step height and particle diameter on the heat transfer and fluid flow of water-nanoencapsulated phase change material over the backward step

In this work, effects of step height and particle diameter on the average heat transfer coefficient, pressure drop and thermal performance index of mixture of water and nanoencapsulated phase change material (NEPCM) over the backward step is examined numerically at different values of Reynolds number, wall heat flux and particle concentration. To validate numerical model, comparisons were made with experimental and other available works in the literature and good agreements were observed. Results show that an increase in the step height causes the heat transfer to decrease and increase thereafter. It is shown that addition of NEPCM to the pure water could enhance the heat transfer rate at high step height. Numerical findings declare that an increase in the particle diameter causes the heat transfer rate to increase and this increase is of little significance at low particle concentration. It is found that the increase in the step height dramatically results in the increase in the pressure drop while an increase in the particle diameter has nearly no effect on the pressure loss. Results indicate that the thermal performance index is a strong function of particle concentration and the best thermal performance index is obtained at low particle concentration.

Effects of step configuration on hydrodynamic performance of one- and doubled-stepped planing flat plates: A numerical simulation

Categorized as one of high-speed marine vehicles, stepped planing hulls have the potential to reach relatively high speed in the sea by decreasing wetted surface. There were and still are some challenges in modeling of these vessels and design of ideal situation of steps. In the current study, a numerical-based method has been used to provide understanding about the effect of step height and its location on hydrodynamic characteristics of double-stepped planing plates. At the first step, one-stepped planing plate is numerically simulated. Results are compared against exiting numerical data, suggesting that results of the current numerical simulation are similar to results of previous numerical simulations. Then, double-stepped planing plates are modeled and pressure distribution, wetted length, free surface elevation and drag over lift ratio are computed. It is seen that, ventilation length behind the step and pressure coefficient are increased when step height of one- and a double-stepped planing plates are increased. It has been shown that, unlike an one-stepped planing plate, drag coefficient of a double-stepped planing plate can be increased when the step height is increased. The effects of the location of the second step on the performance of the planing plate have been explored, showing that this position plays a critical role on hydrodynamic forces. It is demonstrated that when the smallest possible lift force is produced by the middle-body, the plate shows the best performance (highest lift over drag ratio).

Effect of backward facing step on radiation efficiency in a micro combustor

The present study investigates the effect of backward facing step in a micro combustor on blowout limit and outer wall temperature. Effect of equivalence ratio of hydrogen-air mixture and combustor material (i.e. conductive heat transfer coefficient) on emitter efficiency and radiation efficiency perused. In addition, the effect of step height and diameter of combustor are studied. The results show that the presence of backward facing step leads to increase blowout limit and mean wall temperature. Temperature distribution along external wall of micro combustor shows a uniform distribution. It is also observed that combustor with lower step height has higher (mean) wall temperature. Maximum mean wall temperature and radiation efficiency achieved when equivalence ratio is located in lean values. It has been also observed that the wall thermal conductivity has an optimum value to obtain maximum radiation efficiency.

Effect of Step Height On the Aeration Efficiency of Cascade Aerator System Using Particle Image Velocimetry

Aeration is an important parameter in water filtration system as it allows the transfer of oxygen to water through turbulence effect which subsequently increases air entrainment in the water. For water treatment application, aeration efficiency is measured to ensure continuous re-oxygenation of the unfiltered water. Aside from aeration, this paper also studies the flow patterns through the use of particle image velocimetry (PIV) setup. Through the use of real scale down physical model laboratory study is performed using PIV to obtain the velocity profile. These velocity profiles will then be used to calculate the aeration efficiency of the water in a cascade aerator system. Based on the findings, the aeration efficiency obtained from the PIV experiment has a maximum value at the lowest point of the cascade aerator system with a value of 0.0139 due to increase in mass flow rate as it moves through the steps with velocity of 0.418 m/s. Therefore, in the design of a cascade aerator system, it is advisable to increase the number of steps since it will increase the aeration efficiency of the system.

Fitness scores of Indians assessed by the Harvard step test

Background and Aim: The Harvard step test (HST) assesses the physical fitness of individuals. The standard 50.8 cm step of the HST is tailored to western anthropometrics and is rather high for the average Indian whose height is relatively less. Therefore, the height of the step is lower (41 cm) in the modified HST. Even so, it is unlikely that a single step-height will be appropriate for all Indians with different heights. Therefore, the objective of the present study was to verify the same in a group of Indian students with heights ranging from 1.45 to 1.83 m on 41 cm high step. Methods: This study was conducted on 74 healthy subjects in the age group of 17-22 years. Protocol comprises stepping up and down a 41 cm high step at a rate of 30 times/min for the duration, not >5 min. The total duration of stepping exercise and the post-exercise pulse count for 30 s after 1 min recovery was noted and used for calculating the physical fitness index (PFI). Results: The height of subjects positively and significantly correlated to the fitness score and also to the duration of exercise. The mean fitness scores of subjects with height ≥1.66 m were significantly higher than mean scores of subjects with height Conclusion: The shorter duration of effort and the lower score in short subjects may be due to muscle fatigue rather than cardio-respiratory impairment. Our findings suggest that the height of the step used in the HST should be adjusted according to the height of the subject. Considering our small sample size, further studies are required to delineate the effect of step height on PFI in HST.

Study on Effect of Step Height and Load for Large Wind Turbine Spreading Foundation

Aiming at the defects and potential safety hazard in design of wind turbine generator foundation, taking the wind power project in Huitengxile as an example and based on ANSYS platform, 3-D numerical model is established by introducing the nonlinear contact between the stub of tower structure and the foundation concrete, and the contact between the concrete foundation and subgrade, the effect of step height and load on the stress status of spreading foundation for large wind turbine are studied. The research results provide reference for optimization and design of wind turbine generator foundation.

Analysis of turbulent flow and heat transfer over a double forward facing step with obstacles

A numerical study has been conducted to analyze the turbulent forced convection heat transfer for double forward facing step flow with obstacles. Obstacles have rectangular cross-sectional area with different aspect ratio that is located before each step. The numerical solutions of continuity, momentum and energy equations were solved by using a commercial code which uses finite volume techniques. The effect of turbulence was modeled by using a k–ε model. The effects of step height, obstacle aspect ratio and Reynolds number on the flow and heat transfer are investigated. The obtained results show that the rate of heat transfer is enhanced as aspect ratio of obstacle increases and this trend is affected by the step height. Also the results verified that the pressure drop decreases as obstacle aspect ratio increases.

An experimental study of heat transfer to turbulent separation fluid flow in an annular passage

The effect of step height on heat transfer to a radially outward expanded air flow stream in a concentric annular passage was studied experimentally. Separation, subsequent reattachment and developed air flow occurred in the test section at a constant heat flux boundary condition. The experimental investigation was focused on the effect of separation flow on the local and average convection heat transfer. The experimental set-up consists of concentric tubes to form annular passage with a sudden reduction in passage cross-section created by the variations of outer tube diameter at the annular entrance section (D). The outer tube of test section was made of aluminium having 83 mm inside diameter and 600 mm heated length, which was subjected to a constant wall heat flux boundary condition. The investigation was performed in a Re range of 17050–44545, heat flux varied from 719 W/m 2 to 2098 W/m 2 and the enhancement of step heights were, s = 0 (without step), 6 mm, 14.5 mm and 18.5 mm, which refer to d/ D = 1, 1.16, 1.53 and 1.80, respectively. For all cases, an increase in the local heat transfer coefficient was obtained against enhanced heat flux and or Re. The effect of step variation is prominent in heat transfer at the separation region which increases with the rise of step height and it shows a little effect in the redevelopment region. In the separation region, the local heat transfer coefficient increases up to the maximum value at the reattachment point and then decreases gradually in the redevelopment region. The results have been correlated and compared with forced convection heat transfer in annular passage and show a maximum enhancement of 18% ( S max = 18.5 mm) within the range of step height. The present results show good agreement with previous works and have followed similar trends.

Orientation of para-phenylene crystals nucleated on alkali-halide stepped substrates

The influences of substrate steps on crystallographic orientation of para -quaterphenylene ( p -4P) thin films deposited on potassium chloride (KCl) (0 0 1) cleaved in ultrahigh vacuum have been studied in needle-shaped crystals preferentially nucleated at the step edges of the substrates. Surprisingly, most of the crystals nucleated on the so-called tartan zone of the KCl (0 0 1) substrate did not grow epitaxially, but became aligned in the directions of the cleaved steps, indicating the onset of grapho-epitaxy. The effects of step height and width on the nucleation and growth of p -4P crystals have been discussed.

New Scheme for the Computation of Compressible Flows

A new approach for the computation of unsteady compressible flows has been developed. The new scheme employs upwinding of the convective flux based on particle velocity and has been termed the particle velocity upwinding (PVU) scheme. The PVU scheme is an explicit two-step predictor-corrector scheme, in which the convective fluxes are evaluated on cell faces using a first-order upwinding method. The scheme is accurate and stable, giving solutions free from oscillations near the discontinuities without any explicit addition of artificial viscosity. The PVU scheme has an edge over state-of-the-art high-resolution schemes in terms of simplicity of implementation in multidimensional flows and problems involving complex domains. The numerical scheme is validated for both Euler and Navier-Stokes equations. Furthermore, the PVU scheme is used to investigate laminar supersonic viscous flow over a forward-facing step. The results are obtained for M ∞ = 1.5-3.5 in steps of 0.5 and for Re ∞ = 10 4 . Step heights H s of 10 and 20% of the characteristic length of the problem are considered. The effect of step height and the incoming freestream Mach number on the spatial flow structure and on the important design parameters such as wall pressure, skin friction, heat transfer, and length of separated region are investigated.

Three-dimensional convective flow adjacent to backward-facing step - effects of step height

Three-dimensional simulations are presented for incompressible laminar forced convection flow adjacent to backward-facing step in rectangular duct and the effects of step height on the flow and heat transfer characteristics are investigated. Reynolds number, duct's width, and duct's height downstream from the step are kept constant at Re=343, W=0.08 m, and H=0.02 m, respectively. The selection of the values for these parameters is motivated by the fact that measurements are available for this geometry and they can be used to validate the flow simulation code. Uniform and constant heat flux is specified at the stepped wall downstream from the step, while other walls are treated as adiabatic. The size of the primary recirculation region and the maximum that develops in the Nusselt number distribution increase as the step height increases. The “jet-like” flow that develops near the sidewall within the separating shear layer impinges on the stepped wall causing a minimum to develop in the reattachment length and a maximum to develop in the Nusselt number near the sidewall. The maximum Nusselt number, in the spanwise distribution, develops generally in the same region where the reattachment length is minimum. The maximum in the friction coefficient distribution on the stepped wall increases with increasing step height inside the primary recirculation flow region, but that trend is reversed downstream from reattachment. The three-dimensional behavior and sidewall effects increase with increasing step height.

Effect of Step Height on Overhead Drilling in Construction

The purpose of this study was to determine the effect of moving closer to the work while performing overhead drilling. This task was simulated by twenty subjects while standing on either a lower or a higher step of a stepladder. Shoulder load was estimated by root-mean-square amplitude of electromyographic (EMG) activity and cinematographic analysis to determine shoulder joint moment using static link segment modeling. The results indicated that moving closer to the work surface by moving up a step reduces shoulder joint moment and anterior deltoid EMG. However, biceps brachii EMG increased by moving up a step. There was no significant change noted in EMG median frequencies suggesting that fatigue was not a significant factor. We conclude that while moving up a step reduces the muscular load on some muscles and the shoulder joint, other muscles may work harder. There are also safety considerations regarding moving up a step and alternative methods to move closer to the work surface are suggested.

Control Performance of Two-stage Positioning System with Intelligent Control Methods.

As a high precision positioning system with a long working range and high speed, two-stage positioning systems which include the coarse and the fine positioning mechanisms have been proposed. However their most suitable control method has been clarified yet. The purpose of this research is to clarify the most suitable control method for the systems theoretically and experimentally. For this purpose, this paper discusses the performances of the positioning systems with two kinds of intelligent control methods such as the neural control and the fuzzy control ones. Each controller comprises two sub-controllers ; one is for the coarse positioning mechanism and the other is for the fine one. Both controllers are designed by using the dynamic reference models of the mechanism which is expressed on phase plane. Effect of step height, the table mass and constant load changes on the positioning performances are evaluated by simulation and experiment.