Riser Heights Research Articles

Heel Riser Height Influence on Kinematics and Muscle Activity of Ski Mountaineering: A FieldBased Study

Introduction: The ski binding plays an important role in ski mountaineering. When traveling uphill, the binding has an adjustable heel height known as the riser. Previous laboratory research reported joint kinematics and kinetics are influenced by riser height, however little is known about changes to muscle activity associated with differing joint motion. The purpose of this work was to assess riser height influence on kinematics and muscle activity at different slopes during on-snow skiing. Methods: Three female and nine male recreational ski mountaineers (19-26 y) were tested on 5o and 16o gradients using no riser (0 cm) and riser (5.3 cm) at a submaximal 80% HRmax. Each subject used Backland 85 UL skis and Backland Bindings (Atomic Skis, Altenmarkt, Austria). Subjects skied for 6 min at each binding setting with the last 10 gait-cycles evaluating lower limb joint motion gathered from 2D-sagittal plane motion capture. Electromyography (EMG) collected unilaterally on the rectus femoris, biceps femoris, medial gastrocnemius and triceps brachii also. Results: 5o slope: hip range of motion [ROM] decreased (p = .003), ankle ROM decreased (p =.005), stride length decreased (p = .004), RPE increased (p = .02) for riser compared to no riser. At 16o slope: hip ROM decreased (p = .001), and Rating of perceived exertion [RPE] decreased (p =.004) for riser compared to no riser. HR, glide distance, velocity, EMG, and net mechanical efficiency were not different between riser heights on either slope. Conclusion: Lower body joint kinematics, step length and RPE varied significantly with riser height. Kinematic differences did not impact velocity or muscle activity when controlling pace. These results agree with previous findings showing minimal differences in EMG and HR while lower body kinematics and RPE changed with riser height.

Experimental study on the influence of the riser on the gas-liquid flow in the horizontal pipeline of the offshore pipeline-riser system

The study of gas-liquid interface evolution and pressure fluctuation mechanism in the pipeline-riser system is the key to ensuring the safety of oil and gas transportation. This paper investigates the influence of the riser on the gas-liquid interface in the system with a 1657 m pipeline and risers of 16 m, 22 m, and 29 m. In severe slugging, the differential pressure in the horizontal pipeline exhibits a low-frequency large-amplitude fluctuation consistent with those in the riser. During the gas blowdown of the riser, the pressure fluctuation breaks the force equilibrium of the gas-liquid interface and induces numerous liquid slugs in the horizontal pipeline. A strong correlation is found between the differential pressure in the riser and the slug velocity in the horizontal pipeline by the Spearman Rank coefficient. The correlations between the slug velocity and the gas volume fraction and the void fraction under different riser heights are established, and the errors are 15% and 10%, respectively. The linear relationship between the Strouhal number of liquid slugs and the Lockhart-Martinelli parameter is constructed during the gas blowdown.

Heel riser height influence on kinematics and muscle activity of ski mountaineering – A field based study

Introduction The ski binding plays an important role in ski mountaineering. When traveling uphill, the binding has an adjustable heel height known as the riser. Previous laboratory research reported joint kinematics and kinetics are influenced by riser height, however little is known about changes to muscle activity associated with differing joint motion. The purpose of this work was to assess riser height influence on kinematics and muscle activity at different slopes during on-snow skiing. Methods Three female and nine male recreational ski mountaineers (19-26 y) were tested on 5o and 16o gradients using no riser (0 cm) and riser (5.3 cm) at a submaximal 80% HRmax. Each subject used Backland 85 UL skis and Backland Bindings (Atomic Skis, Altenmarkt, Austria). Subjects skied for 6 min at each binding setting with the last 10 gait-cycles evaluating lower limb joint motion gathered from 2D-sagittal plane motion capture. Electromyography (EMG) collected unilaterally on the rectus femoris, biceps femoris, medial gastrocnemius and triceps brachii also. Results 5o slope: hip range of motion (ROM) decreased (p = .003), ankle ROM decreased (p = .005), stride length decreased (p = .004), rating of perceived exertion (RPE) increased (p = .02) for riser compared to no riser. At 16o slope: hip ROM decreased (p = .001), and RPE decreased (p = .004) for riser compared to no riser. HR, glide distance, velocity, EMG, and net mechanical efficiency were not different between riser heights on either slope. Discussion/Conclusion Lower body joint kinematics, step length and RPE varied significantly with riser height. Kinematic differences did not impact velocity or muscle activity when controlling pace. These results agree with previous findings showing minimal differences in EMG and HR while lower body kinematics and RPE changed with riser height.

Effects of riser height and pipeline length on the transition boundary and frequency of severe slugging in offshore pipelines

Investigating the transition boundary and frequency characteristics of severe slugging under different riser heights and pipeline lengths provides important support for the expansion of offshore oil and gas to deeper waters. The visualization research on air-water two-phase flow is carried out in a system with a horizontal pipeline length of 1687 m and riser heights of 16 m, 22 m, and 29 m, and flow pattern maps are plotted. Based on existing experimental data, the database of the flow pattern and slugging frequency in pipeline-riser systems with riser heights of 3–29 m, pipeline lengths of 10–1687 m, and pipe diameters of 25.4–50.8 mm is established. The long pipeline makes the gas pressure growth rate slower than that of the liquid pressure in the riser, which causes severe slugging occurring at higher superficial gas velocity. On the contrary, increasing the riser height causes the boundary of severe slugging to shift to a lower superficial gas velocity. The severe slugging length is greater in the higher riser and longer pipeline system, causing a smaller severe slugging frequency. A correlation for predicting severe slugging frequency at various riser heights, pipe lengths, and pipe diameters is established by employing gas and liquid Froude numbers.

Heel riser height and slope gradient influence the physiology of ski mountaineering-A laboratory study.

In ski mountaineering it is the goal to reach the top of a mountain by sheer muscle force. The specific equipment (flexible boot, only toe fixated binding, and a skin on the ski to prevent from slipping backwards) enables the skier to move up the hill ergonomically, where the heel part of the binding offers a special adaptation possibility. The so-called riser height supports the heel standing height and can be adjusted to individually preferred settings. General recommendations suggest using lower heel support in flat ascents and higher heel support in steep ascents to maintain upright posture and lower the strain. Still, it remains unclear whether the application of riser height affects the physiological response during ski mountaineering. This study was designed to investigate the effects of riser height on physiological response during indoor ski mountaineering. Nineteen participants took part in the study and walked on a treadmill with ski mountaineering equipment. The three available riser heights (low, medium, and high) were applied randomized at 8%, 16%, and 24% gradient. Results show that global physiological measurements like heart rate (p = 0.34), oxygen uptake (p = 0.26) or blood lactate (p = 0.38) values were not affected by changes in riser height. But local measurements of muscle oxygen saturation were affected by the riser height. Additionally comfort and rating of perceived exertion were also prone to changes in riser height. These results suggest differences on local measurements and perceived parameters, while global physiological measurements did not change. The results are in line with the existing recommendations but need to be confirmed in an outdoor setting as well.

Evaluation of Some Uniformity Coefficients for Pressurized Irrigation Systems under Field Conditions in Duhok Governorate (iraqi Kurdistan)

The study was conducted in May–October 2021 within the Duhok University, Iraq, the study was carried out on the land adjacent to the College of Agricultural Engineering Sciences, in the fields of the “Seajay” village latitude 360 55’ 28’’N, longitude 420 52’ 36’’E and 640 (m.a.s.l), the objective of the study was focus on evaluating different uniformity coefficients proposed on investigating the effects of run time and field conditions on the results obtained utilizing those coefficients, a layout of 144 m2 was designed according to the length of lateral lines, 36 catch cans were positioned in a grid of 2 m apart. determining water distribution efficiency affected by different weather conditions during two- daily runs (morning &evening), and two time periods (May & June-July 2021) under operating pressures of (1.0 - 2.0) bar and riser heights of (1.0 - 2 m), solid site sprinkler with a single nozzle type (5mm) was used. The water caught in Cans was subjected to a three-way (ANOVA) table using (LSD) test, the study concluded that riser heights of 1 m had the optimum (CU & DU%) at 2 bar (operating pressure) to reduce water losses, and the results showed that highly significant differences between the means of (CU & DU%) coefficients in (May 2021) at various run times (morning & evening), in time it was shown highly significant differences between the means of all parameters with (PELQ %) coefficients in the (June –July 2021) period. It is not suggested to run the sprinkler irrigation system at wind speeds of (2.6 - 3.6 ms-1)

Heel riser height and slope gradient influence the kinematics and kinetics of ski mountaineering-A laboratory study.

In ski mountaineering, equipment and its interaction with the exercising human plays an important role. The binding, as the crucial connection between boot and ski, must ensure safe fixation during downhill skiing and a free moving heel when walking uphill. Uphill, the binding offers the possibility to adopt the height of the heel (riser height) to personal preferences and the steepness of the ascent. This possible adjustment and its influence on various biomechanical parameters are the focus of this work. For this study, 19 male leisure ski mountaineers were tested on a treadmill, ascending at a fixed submaximal speed (3.9 ± 0.4 km·h−1) at 8, 16, and 24% gradient and with three heel riser heights, low (0 cm), medium (3.0 cm) and high (5.3 cm). The applied biomechanical measurement systems included a 3D motion capture system in sagittal plane, pressure insoles, a with strain gauges instrumented pole, spirometry and a comfort scale. Step length and step frequency were influenced by the riser height and the gradient (p ≤ 0.001). The high riser height decreased the step length by 5% compared to the low riser height over all tested gradients, while steps were 9.2% longer at the 24% gradient compared to the 8% gradient over all three riser heights. The high riser height revealed a force impulse of the pole 13% lower than using the low riser height (p < 0.001). Additionally, the high riser height reduced the range of motion of the knee joint and the ankle joint compared to the low riser height (p < 0.001). Therefore, advantageous settings can be derived, with the low riser height creating proper range of motion for ankle, knee and hip joint and higher propulsion via the pole at 8%, while higher riser heights like the medium setting do so at steeper gradients. These findings are in line with the conducted comfort scale. We would not recommend the highest riser height for the analyzed gradients in this study, but it might be an appropriate choice for higher gradients.

Performance evaluation of indigenous floppy sprinkler irrigation system for various crops water management

Freshwater resources are a natural blessing and vital to life. Water is required in many aspects of life due to its importance in the economy. A Floppy sprinkler system (FSS) is an innovative and unique method for pressurizing irrigation. This method has multiple applications other than traditional methods, which can overcome farmer's issues to adopt the high-efficiency irrigation system. The performance evaluation of two types of floppy sprinklers (imported and indigenous) was the primary objective of this research. Three parameters, application efficiency of the low quarter (AELQ), distribution uniformity (DU), and uniformity coefficient (CU), were evaluated under different levels of riser height and operating pressures. A portable testing bench was designed to determine these parameters and the overall performance of FSS in the agriculture field. The system operated at a different pressure range from 1.5 to 4 bar and riser heights 10ft, 12ft, and 15f for both sprinklers. The results revealed that the system achieved maximum CU, DU, and AELQ at the operating pressure of 2.5 bar and riser height of 10 ft for both types of floppy sprinklers. The corresponding values of CU, DU, and AELQ were 84.5%, 70.7%, and 87.0 % for imported and 82.2%, 67.7%, and 82.5% for indigenous FSS. An overlap simulation model was used to achieve a high percentage of system performance. The results declared that the overlapping between sprinklers should be more than 65% to avoid water losses and minimize the overall system cost.

Using a stair horizontal-vertical illusion to increase foot clearance over an inconsistently taller stair-riser.

IntroductionStair falls can be caused by inconsistent stair dimensions. During ascent, inconsistently taller stair risers lead to reduced foot clearances as the inconsistency goes unnoticed. A stair horizontal-vertical illusion increases perceived riser heights and foot clearance and could offset reduced foot clearances over inconsistently taller risers, though this might impact other stair safety measures.MethodTwelve participants (age: 22 (3) years) ascended a seven-step staircase under three conditions: i) all steps consistent in riser height (consistent), ii) a 1cm increase in step 5 riser height (inconsistent) and iii) a 1cm increase in step 5 riser height, superimposed with a stair horizontal-vertical illusion (illusion). Vertical foot clearance, foot overhang, and margins of stability were assessed over step 4, 5 and 6. Perceived riser height due to the illusion was determined through a computer perception test. A One-Way Repeated Measures ANOVA compared biomechanical variables between conditions. A One Sample t test compared perceived riser height to the true height.ResultsOver the inconsistent step 5, foot clearance reduced by 0.8cm compared to consistent. Illusion increased foot clearance by 1.1cm and decreased foot overhang by 4% compared to inconsistent. On step 4 the illusion led to more anterior instability compared to inconsistent. Illusion and inconsistent led to more mediolateral stability compared to consistent. The illusion increased perceived riser height by 12%.DiscussionFoot clearance reductions over inconsistently taller risers can be offset by a stair horizontal-vertical illusion. Additional benefits included a safer foot overhang and unaffected stability over the inconsistent riser. Changes to step 4 stability might have resulted from leaning forward to look at the step 5 illusion. The stair horizontal-vertical illusion could be a practical solution for inconsistently taller stair risers, where a rebuild is usually the only solution.

Optimization Steel ingot Mould’ Riser Height Based on Solidification Simulation

Solidification process of 13.5t P91 steel ingot with different riser heights were simulated by software and predicted the distribution of shrinkage cavity. The simulation results showed the shrinkage cavity in the precedent ingots is much deeper. The simulation results is agreement well with experiment results. Therefore, the riser height was designed by solidifation simulation and verified by experiments and the results showed that optimized riser height can eliminate shrikage cavity and improve the quality of steel ingot.

The next step in optimising the stair horizontal-vertical illusion: Does a perception-action link exist in older adults?

Tripping on stairs results from insufficient foot to step edge clearance and can often lead to a fall in older adults. A stair horizontal-vertical illusion is suggested to increase the perceived riser height of a step and increase foot clearance when stepping up. However, this perception-action link has not been empirically determined in older adults. Previous findings suggesting a perception-action effect have also been limited to a single step or a three-step staircase. On larger staircases, somatosensory learning of step heights may be greater which could override the illusory effect on the top step. Furthermore, the striped nature of the existing stair horizontal-vertical illusion is associated with visual stress and may not be aesthetically suitable for use on public stairs. These issues need resolving before potential future implementation on public stairs. Experiment 1. A series of four computer-based perception tests were conducted in older (N=14: 70±6years) and young adults (N=42: 24±3years) to test the influence of different illusion designs on stair riser height estimation. Participants compared images of stairs, with horizontal-vertical illusions or arbitrary designs on the bottom step, to a plain stair with different bottom step riser heights and selected the stair they perceived to have the tallest bottom riser. Horizontal-vertical illusions included a previously developed design and versions with modified spatial frequencies and mark space ratios. Perceived riser height differences were assessed between designs and between age groups. Experiment 2. To assess the perception-action link, sixteen older (70±7years) and fifteen young (24±3years) adults ascended a seven-step staircase with and without horizontal-vertical illusions tested in experiment 1 placed onto steps one and seven. Foot clearances were measured over each step. To determine whether changes in perception were linked to changes in foot clearance, perceived riser heights for each horizontal-vertical illusion were assessed using the perception test from experiment 1 before and after stair ascent. Additional measures to characterise stair safety included vertical foot clearance, margins of stability, foot overhang, stair speed, and gaze duration, which were assessed over all seven steps. Experiment 1. All horizontal-vertical illusion designs led to significant increases in the perceived riser height in both young and older adults (12-19% increase) with no differences between age groups. Experiment 2. On step 7, each horizontal-vertical illusion led to an increase in vertical foot clearance for young (up to 0.8cm) and older adults (up to 2.1cm). On step 1 significant increases in vertical foot clearance were found for a single horizontal-vertical illusion when compared to plain (1.19cm increase). The horizontal-vertical illusions caused significant increases in the perceived riser height (young; 13% increase, older; 11% increase) with no differences between illusion design, group or before and after stair ascent. No further differences were found for the remaining variables and steps. Results indicate a perception-action link between perceived riser height and vertical foot clearance in response to modified versions of the horizontal-vertical illusion in both young and older adults. This was shown with no detriment to additional stair safety measures. Further evaluating these illusions on private/public stairs, especially those with inconsistently taller steps, may be beneficial to help improve stair safety for older adults.

Nusselt number and friction factor variations in a capsule heat exchanger filled with eco‐friendly jatropha seed oil–based multi walled carbon nanotubes nanofluid

The present 3‐D numerical paper investigates Nusselt number and friction factor variations in a capsule heat exchanger filled with eco‐friendly jatropha seed oil–based MWCNTs nanofluid. For all studied models, inlet nanofluid temperature is Tin = 310 K, and the hot source with q = 650 W/m2 is adopted. Due to achieve the most efficient Newtonian nanofluid in present study, solid nanoparticles of MWCNT are added to the base fluid in volume concentration of 0.2% to 0.8%. Also, different riser heights (25, 35, and 50 cm) and different emissivity values of capsule walls (ε = 0.3 and 0.7) are studied in this paper. In the current modeling, the SST k – ω turbulence model has been assumed as the turbulence model. Based on achieved results in this paper, the model with capsule angle of β = 30° has better heat transfer than the other studied slopes, which is followed with models with β = 60° and β = 90°, respectively. Also, it is seen that gravity has a significant influence on velocity contours, and in model with β = 90° more pressure drop may be seen, which is followed with models with β = 60° and β = 90°, respectively. Moreover the predicted pressure drop values from inlet to outlet always increase by increase of Reynolds numbers; therefore, there is an optimum Reynolds number during the studied range of flow velocities which leads to the minimum pressure drop penalty. Also, it is realized that usage of nanofluid at higher nanoparticles volume concentrations leads to higher Nusselt numbers during all studied Reynolds numbers. The model with nanoparticles volume fraction of ϕ = 0.8% has the highest values of predicted average Nusselt number which is followed with the models with ϕ = 0.6%, ϕ = 0.4%, and ϕ = 0.2%, respectively. Besides, it is clearly found that usage of walls with different emissivity values has not a significant influence on thermal–hydraulic characteristics of studied capsule heat exchanger.

Optimum Operating Conditions for Impact Sprinkler

Sprinkler irrigation systems can be managed and designed by only conducting an individual sprinkler test in no wind conditions. The present work was conducted to study the effect of different operating pressures and riser heights to determine optimum operating conditions that achieve high application efficiency and wheat production in impact sprinkler system. The coefficient of uniformity (CU,%) was evaluated within the operating pressure range from 100 to 350 kPa, riser heights 1.0, 1.5 and 2.0 m, overlapped from 100 to 20% under square and triangular layouts sprinkler. It was concluded that the operating conditions that achieved high CU was operating pressure of 250 kPa and 1.5 m riser height for impact sprinkler. Information from individual sprinkler test was established to carry out the corresponding overlapping ranged from 20 to 100% in square and triangular layouts sprinkler. Optimal spacing between sprinklers was found to be as 50 to 70% from diameter of throw in square layout. It was found in range of 50 to 80% from diameter of throw in triangular layout sprinkler. The wheat yield was highly affected by water requirements (100, 80 and 60% ETc). The results showed that the average values of total grain and straw yield/fed, increased with increasing ETc from 60 to 100%. The highest yield was achieved with 100% ETc, while, WUE with 80% ETc was the highest value. It could be recommended to apply irrigation water to 100% ETc that has the highest yield of wheat under operating pressure of 250 kPa with good CU for impact sprinkler. On the other hand, adding 80% ETc applied gave the highest values was preferred when the priority to save on the applied water and increase water productivity. Also, layout spacing ≥ 50% from diameter of throw was recommended.

Effect of riser height on rotation uniformity and application rate of the dynamic fluidic sprinkler

AbstractThe objective of this paper was to investigate the effect of riser heights on rotation uniformity and application rate of the newly designed dynamic fluidic sprinkler. The dynamic fluidic sprinkler was tested using different nozzle sizes of 5 and 6 mm. The sprinkler head was mounted on 1.3, 1.5, 1.7 and 1.9 m risers at 90° in the horizontal direction and was placed about 0.9 m above the top of the cans. The following operating pressures were tested: 150 and 200 kPa. A program was written to simulate the non‐uniform of rotation of the nozzle during the full circle‐spraying process. It was found that the riser height had a significant effect on application rate and uniformity. The comparison of standard deviation with different risers showed that differences in standard deviation were much lower for the 1.9 m riser height. The deviation was in the range of 0.14 ~ 0.26, 0.14 ~ 0.42, 0.18 ~ 0.50 and 0.13 ~ 0.69 mm h−1 considering the riser heights of 1.9, 1.7, 1.5 and 1.3 m. For all the nozzle sizes, a smaller standard deviation was recorded under 150 kPa. The deviation range was 0.15 ~ 0.24, 0.17 ~ 0.45, 0.18 ~ 0.45 and 0.2 ~ 0.66 mm h−1 for 1.9, 1.7, 1.5 and 1.3 m, respectively. With respect to nozzle sizes, 5 mm gave better standard deviations and the deviation range was from 0.14 ~ 0.26, 0.15 ~ 0.45, 0.2 ~ 0.7 and 0.23 ~ 0.74 mm h−1 with radial heights of 1.9, 1.7, 1.5 and 1.3 m, respectively. The range of the coefficient of uniformity values for overlapped quadrants for the 5 mm nozzle was as follows: 78% at a spacing of 10 to 72% at 80% overlapped spacing. The highest occurred at 50% spacing and increased with an overlapped spacing of 10 to 50%, ranging from 78 to 87% with an average of 82.5%. © 2020 John Wiley &amp; Sons, Ltd.

An exploration of the differences in hip strength, gluteus medius activity, and trunk, pelvis, and lower-limb biomechanics during different functional tasks

ABSTRACT The purpose of the study was to explore differences in the coronal biomechanics of the trunk, pelvis, hip, and knee joints, and gluteus medius muscle activity (GMed) during walking and step down from two riser heights. Joint kinematics and kinetics from 20 healthy participants were recorded using a 10-camera Qualisys system and force plates, and GMed EMG was recorded using a Delsys Trigno system. Hip abductor strength was measured using a hand-held dynamometer. Pelvic obliquity and lateral trunk bending excursions were significantly higher in walking than in step-down tasks. Significantly greater knee adduction moments were seen during both step-down tasks compared to level walking with significantly greater GMed activity. However, a significant interaction between side and task was seen for hip adduction moment, with step-down tasks showing lower hip moments than during walking, with greater peak hip moments being more apparent in the dominant limb. This suggests the GMed has a greater stabilizing role during the step-down tasks, although walking required a greater mechanical demand. Health professionals should expect to find less excursion of lateral trunk bending in step-down tasks compared to level walking and consider that GMed has different roles in these two tasks.

Combined Resistance and Stretching Exercise Training Benefits Stair Descent Biomechanics in Older Adults.

IntroductionStair descent is a physically demanding activity of daily life and common risk for falls. Age-related deteriorations in ankle joint capacities make stair descent particularly challenging for older adults in built environments, where larger rise steps are encountered. Exercise training may allow older adults to safely cope with the high biomechanical demands of stair descent. However, little is known about the demands of increased rise stairs for older adults, nor the impact of exercise.AimWe investigated whether the effects of lower-limb resistance training would alter joint kinetics and movement strategies for older adults when descending standard rise, and increased rise stairs.MethodsFifteen older adults descended a four-step stair adjusted to standard rise (170 mm), and increased rise (255 mm) on separate visits. Between these two visits, randomly allocated participants underwent 16 weeks of either: resistance exercise training (n = 8) or habitual activity (n = 7). Kinetic data were measured from step-mounted force plates, and kinematic data from motion-capture cameras. Training involved twice-weekly sessions of lower-limb resistance exercises (three sets of ∼8 repetitions at ∼80% three-repetition maximum), and static plantarflexor stretching (three, 45 s holds per leg).ResultsStandard stairs – Peak ankle joint moments increased (p < 0.002) and knee joint moments decreased (p < 0.01) during descent after exercise training. Peak centre of pressure-centre of mass (CoP-CoM) separations increased in posterior (p = 0.005) and medio-lateral directions (p = 0.04) after exercise training. Exercise training did not affect CoM descent velocity or acceleration. Increased rise stairs – Required greater ankle, knee, and hip moments (p < 0.001), peak downward CoM velocity and acceleration (p = 0.0001), and anterior-posterior CoP-CoM separation (p = 0.0001), but lower medial-lateral CoP-CoM separation (p < 0.05), when compared to standard stair descent. Exercise training did not affect joint kinetics or movement strategies.DiscussionExercise training increased the maximum joint ROM, strength and force production of the ankle, and enabled a greater ankle joint moment to be produced in single-leg support (lowering phase) during standard stair descent. Descending increased rise stairs raised the task demand; exercise training could not overcome this. Future research should prioritize the ankle joint in stair descent, particularly targeting plantarflexor torque development across stairs of varying riser heights.

EVALUATING THE PERFORMANCE OF THE POP- UP SPRINKLER

This investigation was carried out at Faculty of Agriculture , Menoufia University, Egypt, on the Pop-Up sprinkler at operating pressures of 1.5 , 2 and 3bar, sprinkler emission angles of 45o , 90 o ,135 o, 180 o ,225 o, 270 o , 315 o and 360o and riser heights of 0.15 ,0.75 and 1.25 m . Discharge, uniformity distribution, coefficient of variation and water losses percent of the sprinkler due to evaporation and water drift were determined . Results indicated that, when pressure decreases, discharge and coefficient of uniformity decrease . The percentage of the average decreasing for discharge were 28 and 42% and decreasing of coefficient of uniformity were 12.05 and 23.77% when using the operating pressures of 2 and 1.5 bar compering with 3 bar resp. But increase coefficient of variation and water loss percent due to evaporation and water drift .Moreover, increasing the riser height at the sprinkler emission angles the discharge and the coefficient of uniformity decrease . When angle increase from 45o to 360o the discharge and coefficient of variation increase from o.115 to 0.362 m3 /h and from 14.54 to 30.98 % resp. ,while coefficient of uniformity and water loss percent .decrease from 80.46 to 74.38 % and from 17.85to 11.21 % resp. Due to interaction between the operating pressure 3 bar and height riser of 0.15 m at emission angle of 360o gave the highest value of the discharge , while at the angle of 45 o gave the highest value of coefficient of uniformity.

Computational fluid dynamics on the hydrodynamic characteristics of the conical cap tray

This paper addresses an investigation on the hydrodynamic behavior of a new type of cap trays called conical cap tray (ConCap tray). A 3-D computational fluid dynamics model was developed to predict the hydrodynamics of the ConCap tray which is operated in the spray regime. The model considers two phase flow of gas and liquid in a VOF-like code framework. The homogeneous multiple size group model (MUSIG model) and shear stress transport (SST) turbulence model were implemented. Detailed insights into the hydrodynamic behavior of the inside of the cones were obtained. The relation between velocity, pressure and cross section area of the flow inside the cone also was formulated. The computational fluid dynamic (CFD) results show that the pressure variation in the cones forces the liquid on the tray to be highly turbulent, which leads to deform the interface to break up. Effect of different riser heights was also studied by CFD simulations. The results show that the riser height has a significant role in the hydrodynamics of the tray, especially in uniform gas distribution in the tray and reducing weeping rates.

Three-component solids velocity measurements in the outlet section of a riser.

Coincident (simultaneous) three‐component particle velocity measurements performed using two laser Doppler anemometry probes at the outlet section of a 9 m high cylindrical riser are for the first time presented for dilute flow conditions. Near the blinded extension of the T‐outlet a solids vortex is formed. Particle downflow along the riser wall opposite the outlet tube is observed, which is restricted to higher riser heights at higher gas flow rates. Increased velocity fluctuations are observed in the solids vortex and downflow region as well as at heights corresponding to the outlet tube. Contrary to the rest of the riser, in the downflow region time and ensemble velocity averages are not equal. Given the local bending of the streamlines, axial momentum transforms to radial and azimuthal momentum giving rise to the corresponding shear stresses. Turbulence intensity values indicate the edges of the downflow region. © 2016 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 62: 3575–3584, 2016

Age-related differences in dynamic balance control during stair descent and effect of varying step geometry

The incidence of stairway falls and related injuries remains persistently high; however, the risk of stair injuries could be reduced through improved stairway design. The current study investigated dynamic balance control during stair descent and the effects of varying the step geometry. Data were collected from 20 healthy young and 20 older adults as they descended three staircases (riser heights of 7, 7.5 and 8 inches (178, 190 and 203 mm, respectively)). At each riser height, the tread run length was varied between 8 and 14 inches (203 mm and 356 mm) in one-inch (25 mm) increments. Kinematic data provided measures of segmental and whole-body dynamic control. Results demonstrated that older adults had greater lateral tilt of the upper body than young adults, but actually had larger margins of stability than the young in the antero-posterior direction as a result of their slower cadence. Nonetheless, for both age groups, the longer run lengths were found to provide the largest margins of stability. In addition, increase in run length and decrease in riser height tended to reduce forward upper body tilt. These results help to explain the underlying biomechanical factors associated with increased risk of falls and the relationship with step geometry. Considering the importance of stair ambulation in maintaining independence and activity in the community, this study highlights the definite need for safer stair design standards to minimize the risk of falls and increase stair safety across the lifespan.