Radiating effect of participating media in a flameless industrial reactor

A 3D multi-physical numerical model concerning fluid-dynamical and thermo-chemical behaviour of a flameless reactor is presented in this communication. The analysed industrial device exploits a recent combustion technique that seems to largely hinder thermal NO x formation. Modelling and computations are carried-out by using a multi-physical FEM commercial software. The swirling jet used for combustive injection is firstly analysed, then the entire reactor volume is considered for simulations. The fluid-dynamics of the process is based on a k - e turbulence model, coupled with four diffusion-transport equations whose the first one characterises the temperature, while the remaining three are related to the concentrations of the chemical species involving in the process. In order to consider the radiating effects of participating media inside the combustion chamber, the Rosseland approximation is invoked in solving the energy equation. Results principally highlight the occurrence of a Reverse Flow Zone closed to the inlet section of the swirling injection system and a flat temperature profile characterising thermal distribution throughout the control volume of the reactor. These findings are in good agreement with experimental data concerning similar operating devices

A METHOD FOR THE PERFORMANCE EVALUATION OF JUMPING HEADERS IN SOCCER

The aim of the present work was to develop a method for the evaluation of soccer heading performance in jumping headers by means of a stereophotogrammetric system. Three non-professional players were involved in this pilot study. The attention was focused on the following variables: the player’s jump height at the impact instant, the ball velocity variation and the initial ball angle after the impact with the forehead of the player. The analysis of these parameters permitted to characterize the biomechanical technique and the performance ability of each player in such a way that a trainer can define individual procedures to improve the efficacy of this fundamental skill in soccer. Finally an Elevation Index (E.I.) was developed to compare the players performances and to draft a ranking between them

Biomechanical comparison of shorts with different pads: An Insight into the Perineum Protection Issue

An intensive use of the bicycle may increase the risk of erectile dysfunction and the compression of the perineal area has been showed to be a major mechanism leading to sexual alterations compromising the quality of life. Manufacturers claim that pads contribute to increase cyclists perineal protection ensuring a high level of comfort. To investigate the influence of various cycling pads with regard to perineal protection and level of comfort. Nine club road cyclists rode 20 min on a drum simulator, located at the Nutrition and Exercise Physiology Laboratory, at a constant speed and gear ratio wearing the shorts with 3 cycling pads of different design and thickness: basic (BAS), intermediate (INT), and endurance (END). Kinematics and pressure data were recorded at min 5, 15, and 20 of the test using a motion capture system and a pressure sensor mat. The variables of interest were: 3-dimensional pelvis excursions, peak pressure, mean pressure, and vertical force. The comfort level was assessed with a ranking order based on the subjects' perception after the 20-min trials and measuring the vertical ground reaction force under the anterior wheel as well as the length of the center of pressure (COP) trajectory on the saddle. Results showed that the vertical force and the average value of mean pressure on the saddle significantly decreased during the 20-min period of testing for BAS and END. Mean peak pressure on the corresponding perineal cyclist area significantly increased only for BAS during the 20-min period. Interestingly objective comfort indexes measured did not match cyclists subjective comfort evaluation. The lower capacity of BAS to reduce the peak pressure on the corresponding perineal area after 20 min of testing, together with its positive comfort evaluation, suggest that a balance between protection and perceived comfort should be taken into account in the choice of the pad. Hence, the quantitative approach of objective comfort indexes introduced in this study could be helpful for manufacturers in the development of their protective pads

Behaviour of an instrumented anthropomorphic dummy during full scale drop tests

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EVALUATION OF SPRINT BIOMECHANICS BY MEANS OF AN INSTRUMENTED TRAINING SLEDGE IN SOCCER

The aim of the study was the functional evaluation of sprint biomechanics by means of an instrumented training sledge in a soccer field. In particular, peak values of the horizontal ground reaction force generated in the first 6 thrusts were estimated after measuring the instantaneous cable tension and the sledge acceleration with a data acquisition system installed on the sledge. Three soccer players were asked to perform 3 couples of 30m sprints (starting once with the left and once with the right leg) while pulling the training sledge: the sledge mass increased in three levels (11.5kg, 16.5kg, 21.5kg). The athletes performed also Bosco tests in monolateral CMJ. Differences in force values between the two legs were more evident after the sledge functional testing in the field than after Bosco monolateral CMJ: the method can suggest functional training procedures to improve the strength of the weak leg and running coordination

CORRELATION BETWEEN SUPPORT FOOT PLACEMENT AND GOAL ACCURACY FOR INSTEP KICKS IN THE SOCCER FIELD

The aim of the present work was to evaluate the correlation between the placement of the support foot on the ground and the precision of the shot: the placement of the support foot relative to the ball was supposed to have an effect on the shot precision for a given target. The goal was divided with a visual grid enabling to identify six possible targets of the shot, high/low for vertical placement and left/center/right for horizontal placement. Skilled players were asked to perform repetitive penalty instep kicking in the soccer field with a defined target such as high/left or low/right: ground reaction loads were recorded by means of a force platform installed in a suitable board and the movement was video recorded. The position of COP at the kick instant with respect to the ball and the average trajectory of COP on the platform resulted to be correlated with successful target in such a way that training procedures can be defined to improve the player coordination for precision shooting. Finally, differences between free kicking and kicking with a goalkeeper were recorded, enabling to analyze a realistic player behaviour in the study