Increase In Horizontal Velocity Research Articles

Distribution of phosphorus in bed sediment at confluences responding to hydrodynamics

Knowledge of the distribution of contaminants at channel confluences is critical for understanding their transport and dwelling at river networks where flow confluences constitute the key nodes. Flume experiments were conducted to study the distribution of phosphorus adsorption in surface sediment under complex hydrodynamics at channel confluences. The influence of the discharge ratio of the tributary discharge to the main stream discharge was also investigated. The results showed that the horizontal velocity and vertical velocity of flow are the dominant factors affecting the distribution of phosphorus adsorption. Flows with a larger horizontal velocity are not beneficial to phosphorus adsorption on sediment and thus low- and high-adsorption strips of phosphorus occur in the maximum velocity zone and the flow separation zone, respectively. Downwelling flows are beneficial to phosphorus adsorption on sediment as they can enhance phosphorus exchange between overlying water and the bed sediment. A small flow penetration with a small discharge ratio causes a decrease in vertical velocity in the separation zone as well as the strong intrusion of a helical cell into the bottom of this zone, which results in an increase in horizontal velocity near the bed and consequently the phosphorus adsorption is largely restricted.

Performance Analysis of Men's 110-m Hurdles using Rhythmic Units

Objective: This study aimed to create a strategic training method to enhance optimal athletic ability using information from 1H to 10H rhythmic units. Method: Top three world class athletes and three national winners of 110-m hurdle finals from the 2010 Daegu International Athletics Competition and 2017 National Athletics Championship, respectively, were selected. To analyze the kinematic variables, Dartfish 9.0 was used for two-dimensional analysis. Results: Regarding the interval time from the start to the finish line, the national athletes took less time during the pure acceleration phase (start to 1H) than the foreign athletes. The horizontal velocity increase was slower after 1H; the national athletes showed a lack of ability to accelerate at the interval phases. Moreover, the hurdle clearance time between phases was longer in the national athletes than in the foreign athletes and lacked consistency. Conclusion: The national athletes lacked the ability to accelerate at the transition, maximum rhythm, rhythm maintenance, and re-acceleration phases and showed a longer hurdle clearance time. If technical improvements and strategic training methods using rhythmic units are applied for hurdling motions, the national athlete''s hurdling abilities, performance, and consistency could improve.

Motion of Williamson Fluid over an Upper Horizontal Surface of a Paraboloid of Revolution due to Partial Slip and Buoyancy: Boundary Layer Analysis

In this article, the motion of a non-Newtonian visco-inelastic fluid over an object that is neither a cone/wedge nor horizontal/vertical is presented. It is assumed that partial slip and buoyancy induces the flow of Williamson fluid over this kind of object herein referred to as an upper horizontal surface of a paraboloid of revolution. Considering the relationship between the thicknesses of the object and velocity index; the relevance of partial slip at the leading edge is significant and illustrated in this article. The governing equation which models the flow is non-dimensionalized and parameterized. The corresponding dimensionless equations are solved numerically using shooting technique along with fourth order Runge-Kutta integration scheme. Due to the presence of partial slip and thermal jump, increase in horizontal velocity at the wall is ascertained. The decrease in local heat transfer rate is ascertained within large interval next to the surface of a paraboloid of revolution in the absence of partial slip and thermal jump. A significant decrease in temperature distribution near the surface of an upper horizontal surface of a paraboloid of revolution is guaranteed with an increase in thermal buoyancy parameter in the presence of thermal jump.

The impact of trough geometry on film shape. A theoretical study of droplets containing polymer, for P-OLED display applications

For P-OLED display fabrication, it is important to control the final film shape, arising from drying of volatile droplets containing polymer. Due to peripheral pinning and subsequent outward capillary flow, a coffee-ring typically develops. This is inconvenient since a spatially uniform height, above the substrate, is required to ensure uniform current across the device. Typically the droplets are deposited inside a trough-like structure on the substrate. We present a thin-film lubrication model that tracks the drying dynamics through to the final film shape. The governing equations are derived and solved numerically. We investigate the effect of the trough’s depth and the slope of the walls. Increasing the depth or the wall’s gradient increases coffee-ring formation. This is due to an increase in horizontal velocity, caused by the substrate’s shape as well as delayed gelation of the polymer. The latter allows the outward capillary flow to act for a longer time, before the height becomes fixed.

Poster Session II, July 14th 2010 — Abstracts: How the swimmer could improve his track start using new Olympic plot

In sprint swimming races, performance has been strongly linked to start performance. The Start is defined as three phases: the impulse phase on the starting block (including reaction time), the flight phase, and the underwater phase. Results of studies conducted since the 70’s defined that velocity, as well as minimized hydrodynamic resistances when entering in the water have direct impact on the underwater phase. The aim of this study is to define the impulse, the flight and the anthropometric characteristics of the swimmer that can improve the beginning of the underwater phase of the swimming start. Swimmers of national level were asked to perform competitive track starts as efficiently as possible on new Olympic starting plot. Starting bloc position on the starting plot, height, mass and percentage body fat of each swimmer were measured. A two dimension direct linear transformation (DLT) method was used to calculate the hand and hip landmarks coordinates in space. Using the coordinates of the landmarks, kinematics variables at impulse and flight phases were defined. Stepwise linear regression analysis shows that increase of horizontal velocity at take off and the flight distance (FD) associated with decrease of vertical velocity at water entry (VZwe) are the best kinematics’ predictors to improve the total velocity at water entry (V2Dwe) (R2=0.66). There was no significant relation between V2Dwe and bloc position on the plot. Stepwise linear regression analysis shows that increase of mass is the best anthropometrics’ predictor to improve the horizontal velocity at take off (R2=0.45). For the other dependant variables (V2Dwe′, VZwe′, FD) the physical variables are not relevant (R2<0.4). In conclusion, this study shows that it can be possible to realize an accuracy training testing of the impulse and the flight phase of swimming start using one camera, two landmarks and two dimension DLT’s algorithm. If the underwater phase is the most relevant of the swimming start, the swimmer could improve the efficiency of this phase by increasing the total velocity at entry. This study shows that the position of the starting bloc of the new Olympic plot doesn’t influence the efficiency in track start. During a track start, increasing the horizontal velocity at the impulse phase associated with increasing the fight phase and decreasing the vertical velocity at water entry; seems to be the best predictors to improve the efficiency of the underwater phase.

Theoretical Studies of Convectively Forced Mesoscale Flows in Three Dimensions. Part II: Shear Flow with a Critical Level

Abstract Convectively forced mesoscale flows in a shear flow with a critical level are theoretically investigated by obtaining analytic solutions for a hydrostatic, nonrotating, inviscid, Boussinesq airflow system. The response to surface pulse heating shows that near the center of the moving mode, the magnitude of the vertical velocity becomes constant after some time, whereas the magnitudes of the vertical displacement and perturbation horizontal velocity increase linearly with time. It is confirmed from the solutions obtained in present and previous studies that this result is valid regardless of the basic-state wind profile and dimension. The response to 3D finite-depth steady heating representing latent heating due to cumulus convection shows that, unlike in two dimensions, a low-level updraft that is necessary to sustain deep convection always occurs at the heating center regardless of the intensity of vertical wind shear and the heating depth. For deep heating across a critical level, little change occurs in the perturbation field below the critical level, although the heating top height increases. This is because downward-propagating gravity waves induced by the heating above, but not near, the critical level can hardly affect the flow response field below the critical level. When the basic-state wind backs with height, the vertex of V-shaped perturbations above the heating top points to a direction rotated a little clockwise from the basic-state wind direction. This is because the V-shaped perturbations above the heating top is induced by upward-propagating gravity waves that have passed through the layer below where the basic-state wind direction is clockwise relative to that above.

Hippopotamus Underwater Locomotion: Reduced-Gravity Movements for a Massive Mammal

Use of the aquatic environment by hippopotami (Hippopotamus amphibius) allows locomotive styles impossible to achieve on land by such heavy animals. Videos of the underwater locomotion of 2 hippopotami were analyzed frame by frame. Average horizontal velocity underwater was 0.47 m/s. Hippopotami used a gait underwater that was similar to a gallop with extended unsupported intervals. Ground contact time decreased with increasing horizontal velocity, vertical displacement during the unsupported intervals increased with an increase in ground contact time, and time between consecutive footfalls decreased with an increase in horizontal velocity. Hippopotami use an unstable gait underwater, which is facilitated by the increased buoyancy of water. Despite restrictions to movement on land due to its massive weight, locomotion of the hippopotamus underwater is analogous to movement in a microgravity environment.

Damage Mechanism of Armor Blocks at Toe of Rubble Mound Foundation of Composite Breakwater

The Hudson equation is, in general, employed to estimate the minimum weight of an armor unit on rubble mound foundation. However, the damage of the units is occasionally found at the toe of the foundation while the weight of armor units is larger than the one calculated by the Hudson equation. This paper aims to elucidate the damage mechanism of armor blocks at the toe of rubble mound foundation of a composite caisson-typ. breakwater by performing hydraulic model experiments and numerical computations with a numerical wave flume “CADMAS-SURF” under irregular wave actions. It is found from the numerical and experimental results that the increase of horizontal velocity and the decline of wave pressure in the vicinity of the blocks cause the block damage at the toe of the foundation.

Flow Resistance and Associated Sedimentary Processes in a Spartina maritima Salt-Marsh

The vertical accretion of salt marshes is mainly due to flow reduction and wave damping by vegetation. However, the details of the hydrodynamics are only partially understood, and have been studied mainly in the laboratory. This study presents detailed field investigations of the water flow in a Spartina maritima salt-marsh in the Ria Formosa, a shallow, meso-tidal lagoon in Southern Portugal. Detailed velocity profiles were obtained within and above the 30 cm high canopy using a high-precision velocimeter. Results show that the influence of the bottom becomes negligible a few centimetres above the bed, and that the flow depends on the vegetation density at each level of the canopy. When the canopy is partially emergent or is only slightly submerged, the upward increase of horizontal velocity is roughly linear. A more drastic flow reduction exists when the canopy is well submerged, with a slow, nearly constant velocity in the denser part of the canopy and a faster, logarithmic shaped velocity profile above. This dampening effect of the vegetation is expected to promote sedimentation. However, the short-term sedimentation rate obtained with sediment traps during fair-weather conditions is usually lower in the Spartina marsh than in the surrounding areas. Therefore, the effect of the Spartina canopy for sediment accumulation seems to be more that of erosion protection during storms than of sedimentation enhancement during normal conditions. Using these results, a simple conceptual model is proposed for the sedimentary processes taking place in the intertidal areas of the studied lagoon.

Organization of Tropical Convection in Low Vertical Wind Shears: The Role of Cold Pools

Abstract An investigation is conducted to document the role convectively generated cold pools play in determining the spatial organization of tropical deep convection. Using a high-resolution cloud-resolving model, the evolution of cold pools produced by deep convection is examined, in the situation of limited large-scale wind shear, and a homogeneous underlying sea surface temperature. Ignoring the cold pools resulting from multiple deep convective events, the mean model cold pool attained a minimum temperature and water vapor mixing ratio depression of 1 K and 1.5 g kg−1, respectively; a horizontal velocity increase of 4.8 m s−1; and the latent and sensible heat fluxes are increased by a factor of 1.9 and 2.6, respectively. The cold pools had a mean lifetime of approximately 2.5 h and attained maximum radii ranging from 3 to 18 km, with a mean of 8.6 km. Taking the organization of convection into account, these figures are consistent with observational studies of convective wakes. The composite cold poo...

Contribution of the lower extremity joints to mechanical energy in running vertical jumps and running long jumps

The energy contribution of the lower extremity joints to vertical jumping and long jumping from a standing position has previously been investigated. However, the resultant joint moment contributions to vertical and long jumps performed with a running approach are unknown. metatarsophalangeal joint to these activities has not been investigated. The objective of this study was to determine the mechanical energy contributions of the hip, knee, ankle and metatarsophalangeal joints to running long jumps and running vertical jumps. A sagittal plane analysis was performed on five male university basketball players while performing running vertical jumps and four male long jumpers while performing running long jumps. The resultant joint moment and power patterns at the ankle, knee and hip were similar to those reported in the literature for standing jumps. It appears that the movement pattern of the jumps is not influenced by an increase in horizontal velocity before take-off. The metatarsophalangeal joint was a large energy absorber and generated only a minimal amount of energy at take-off. The ankle joint was the largest energy generator and absorber for both jumps; however, it played a smaller relative role during long jumping as the energy contribution of the hip increased.

Boundary layer models of ocean floor spreading

The equations of conservations of momentum and energy scaled with the characteristic values of the mantle indicate the presence of the upper boundary layer to produce the estimated rate of the ocean floor spreading by convection and the importance of the frictional heating. The depth of the upper boundary layer can be estimated from the balance of the viscous force with the horizontal pressure gradient at the sea floor. It is of the orders of 100 km and becomes deeper for the Pacific than for the Atlantic Ocean and also with frictional heating than without it. The frictional heating increases the surface heat flow of the heat conduction by ten to twenty percent for the Pacific Ocean but only by a few percent for the Atlantic Ocean. The similarity solutions are determined for the temperature and horizontal velocity in the upper boundary layer. These solutions are expressed in power series of the variabley x−n, wherex, y, andn are horizontal and vertical coordinates and numerical constant, respectively. Both temperature and horizontal velocity within the boundary layer are higher for the Pacific than for the Atlantic Ocean. When a larger viscosity is applied, it causes the increase of horizontal velocity below the surface because of the surface boundary conditions of the finite velocity and of vanishment of the velocity shear. The higher horizontal velocity generates higher temperature because it advects hotter material from the mid-ocean ridge site. The direct effect of frictional heating on the temperature distribution of the similarity solution is almost negligible, since the shear zone is deep and near the lower boundary of the upper boundary layer. In the similarity solution, the surface heat flow which is increased by the frictional heating is given as the boundary value. The effect of the frictional heating is important below the mid-ocean ridge.