This paper presents an aero-acoustic experimental study of the squirrel cage fan where the relation between unsteady fluid flow and noise generated in the fan was investigated. Fan performance and noise are compared for different inlet geometries. Noise pressure measurements in the exit channel of a fan are presented together with laser Doppler velocity measurements outside the rotor. Velocity measurements show that the largest fluctuations happen just after the inlet and close to the cut-off. The power spectra of velocity components near the inlet and behind the cut-off are higher than other circumferential and axial positions. Blade passing frequency is evident in noise and velocity data with a considerable volume of white band noise. It fades at locations with no flow through the rotor.

The Research has shown that the primary sound source in centrifugal turbomachines is the Blade passing frequency noise, which is caused by due to impac rotor exit flow with the volute and the wild pressure fluctuations. In this paper, a centrifugal blower with forward facing Blades has been selected and the sound created by it in the output channel has been investigated in different operating conditions. Also, to study the relationship between the pressure fluctuations on the volute and the radiated sound, the amplitude of the pressure fluctuations in different volutes areas (from the cutt-off to the near-outlet channel) has been investigated. The results show remarkable noise at the Blade passing frequency in all fan state modes. It also increases by increasing the fan outlet flow. The pressure fluctuations on the volute are also evidence of pressure in the Blade passing frequency. The intensity of this pressure is reduced far from the volute tongue, which means that the flow of jet in those areas is lower. Also, at 300 degrees from the cut-off, a strong pressure fluctuation was observed that is the second primary source of the tonal sound (other than the cut-off).

Introduction: Usually osseointegration takes between three to six months after implant placement but patients are interested to have early loading. There are no definitive criteria for measuring bone mineral density (BMD), insertion torque (IT) (final torque force) and resonance frequency analysis (RFA) (primary implant stability) to determine exact loading time based on the relationship between the above-mentioned parameters. The aim of this study was to determine the relationship between IT, RFA and BMD in screw-type implants.Materials and Methods: This clinical trial was conducted on 18 patients who were candidates for ITI implant placement. Written consent was taken and jaw bone density was determined via a digital radiography technique before surgery. After implant placement, RFA and IT were measured. Fifty-five ITI implants of the total 62 implants placed were evaluated; the implants were 12 mm long with a diameter of 4.1 mm. Data was analyzed with Pearson’s test using SPSS.15 software (a=0.05).Results: There was a significant relationship between IT, RFA and BMD. Pearson’s test showed a correlation coefficient of 0.872 to 0.789 between the three parameters, indicating a strong relationship between them. The mean bone density was 1.468±0.042 g/cm2; the mean RFA was 66.01±2.2 ISQ and the mean IT was 34.62±3.33 N/cm2.Conclusion: Based on the results of the present study there is a significant relationship between, IT, RFA and BMD (p value=0.001).

There are many conditions in open channel flows where the steady flow of water passes through a cluster of vertical cylinders. These vertical cylinders may represent piers of bridge, jetty or vegetation on the floodplain of rivers. Where flow passes from a cylinder, periodic vortex shedding occurs downstream from the cylinder. In this study the wooden circular cylinders with different diameters were screwed into the bed of the flume at different setting up patterns and spacing. The waves were produced from the periodic forces created by the vortex shedding from the cylinders. The transverse waves with maximum amplitude appear, when natural frequency of water waves equals to frequency of vortex shedding. The major purpose of this study is to compute of Strouhal Number in flow of water passes through vertical cylinders. The values of Strouhal Numbers calculated from Fitz-Hugh's graphs and Lienhard's graphs were not equal to the measured Strouhal Numbers. Thus dimensional analysis is used for this proposition. To find a proper equation for Strouhal Number in water, the effective parameters on Strouhal Number are recognized and analyzed. Finally new equations are proposed for determination of Strouhal Number in open channels flow.

The Blades of wind turbines are the most important parts in producing power output. In this study, a section of a 660 KW wind turbine Blade will be installed in Iran in near future was tested in a wind tunnel. In addition to steady tests, various unsteady tests including the effects of reduced frequency mean angle of attack, and amplitudes were carried out. The preliminary results show strong effects of reduced frequency on the aerodynamic coefficients of the airfoil. Moreover, increasing the reduced frequency delays dynamic stall angle of attack but increases lift and drag coefficients compared to the static results. Further, the values of the aerodynamic coefficients in the upstroke motion (increasing angle of attack) are different form their corresponding values in the downstroke (decreasing angle of attack). These differences create a hysteresis loop where its width and shape are strong functions of reduced frequency, mean angle of attack, and amplitudes.

Nowadays, the issue of energy supply is one of the key challenges. In recent years, in order to search for sustainable, renewable, and low cost energy sources, energy harvesting from vibrations caused by fluid flow has great importance. In the present study, an energy-harvesting device from airflow vibrations consisting of a piezoelectric Blade has been studied. The Blade is exposed to fluid flow at a certain distance downstream of a circular cylinder, and its behavior is simulated using a UDF code implemented to the Fluent software. According to the results of this study, the mass of the Blade containing the piezoelectric layer is one of the most important factors affecting the rate of energy harvesting and increasing it will improve the output voltage. Also, in this study, the special focus is on investigation the possibility of resonance phenomenon with a change in the mass of the Blade tip. It is observed with increasing mass on the Blade tip from 0.9 to 1.5 g, due to the reduction of the natural frequency of the Blade, the velocity of the fluid flow required for the resonance phenomenon can be reduced by up to 20%. In this research, the effect of changes of mass which is added on the tip of the Blade was investigated for 3 different values, which was not observed in the previous researches..

Allergic diseases are prevalent in children and their prevalence and severity are different in dissimilar areas of the world. Many studies have been carried out regarding the inspection of the causative environmental factors such as air, foods and environmental allergens. In this study, using the ISAAC standardized method, the relation between asthma and allergic rhinitis symptoms with the kind of fuel consumed at homes and the frequency of lorry passing through the streets next to the houses in 3000 children aged 6-7 years and 3000 children 13-14 years was investigated. The results indicated that in the children aged 6-7 years, the prevalence of asthma and allergic rhinitis had a meaningful relation with the type of fuel consumed at homes (P<0.05), so that the less pollutant fuel resulted in less symptoms. The evidence suggested that in both age group, when there was lorry passing all day long, there were more wheezing and allergic rhinitis symptoms, and the difference was meaningful regarding allergic rhinitis (P< 0.05). The study reveals that indoor and outdoor air pollution is associated with increase in the prevalence of allergic diseases in children. Therefore, it seems that these types of air pollution can be a cause of increase of the allergic cases in childhood.

Impellers with splitter Blades are used for pumps and compressors in the design of turbomachines. Design parameters such as the number of Blades, Blade discharge angle and impeller discharge diameter impact affect pump performance and energy consumption. In this study, the effect of the number of Blades (z=5, 6, and 7), Blade discharge angles (β 2b=25 , and β 2b=35 ) and splitter Blade lengths (40, 55, 70, and 85% of the main Blade length) on Deep Well Pump (DWP) performance has been studied experimentally. In the experiments, pump casing, Blade inlet angle, Blade thickness, Blade width and impeller inlet and discharge diameters have been kept fixed while other parameters such as the number of Blades, Blade discharge angles and splitter Blade lengths have been allowed to vary. As a result of the experimental study, the highest efficiency of all the impellers for best efficiency point (b. e. p) has been obtained on the impeller with the number of Blades z=6, Blade discharge angle  2b=25 and 85% splitter Blade addition compared to impellers without splitter Blades.

The helicopter rotor Blade flapping results in a helicopter rotor symmetry lift and has a significant impact on stability and control. In this paper, the modeling of helicopter flapping in the presence of aerodynamic forces and moments and the effect of offset, Blade torque, hinge resistant spring, Blade geometry, natural frequency effect, and forward ratio to achieve reliable relief from flapping was investigated. In the simulation, the effects of small and large flapping angles and the role of offset on the momentum entered on the Blade, as well as the role of the forward ratio in moments were investigated. Different models of flapping dynamics and equations for the flight of a hover and cruise helicopter are fully presented and all of the important issues are examined for a numerical example. Also, the effect of non-uniform flow in the flapping equations of the Blade is the effect of the natural frequency of the flapping motion with the Blade offset. This leads to increasing the accuracy in modeling the phenomenon of flapping on a helicopter. Simulation results show the importance and impact of offsets, moments and forces imposed on the Blade in the motion of the flapping, which leads to an increase of accuracy in modeling.