We studied the effect of permeability on wave reflection by Mansard method with 3 wave height meter sensors applied in wave flume. By increasing of fluid head, some of it penetrates into bed which called suction. In this case streamlines are close to bed and velocity near bed increases that result in bed stress increases by factor 2.5. On the other hand, by decreasing the fluid head, it leaks out of bed, called injection, which results in -decreased mean velocity near bed and 70% decrease in stress. Reflection factor of WAVES decreases at coasts for the same permeability by increasing wave steepness. By increasing of wave breaking similarity parameter, the wave reflection parameter increases about 2 times. We conclude that the reflection parameter reduced by increasing permeability . We used 7 regular WAVES with range of steepness from 0.02 to 0.04 in deep water to study effects of permeability on wave reflection as well. As for the bed currents, by increasing its slope to (1:3), for very low, low, middle, and high permeabilities, results are in agreement with the previous studies, but there is a slight difference in current shape.  

The present paper, at first, it calculates effect of INTERNAL WAVES on sound speed and time stability of sound channel specifically at effect zone of WAVES. Then, it discusses the modal solutions of governing equations on the INTERNAL WAVES with finite differences method and based on numerical ideas extant in normal modes method. Next, it applies the changed sound speed profile and the density in parabolic equations method. Also, it considers conditions of effect of the INTERNAL WAVES on sound speed variations and on the time stability of sound channels. In the end, with comparison of the effect of these WAVES on the sound propagation, it is analyzed the change of the procedure of acoustic WAVES simultaneous in diagrams with propagation state without effect of the INTERNAL wave which the gotten results confirm the method efficiency.

For calculating the acoustic pressure due to sound propagation at sea using usual methods (pressure variations signals), knowing the density distribution and consequently, changes the speed of sound in the environment is very important. Many environmental factors affect the distribution of the density at sea, depending on environmental conditions and geographic locations and the weaknesses of each of them are different. One of them is INTERNAL WAVES which usually cause temporal and spatial changes and consequently affect the acoustic wave propagation in the ocean. INTERNAL WAVES can be generated by tidal currents over sea floor sloping that is very common in the stratified oceans. Results of study in some researches showed that INTERNAL WAVES can affect the sound WAVES in two ways: 1-INTERNAL WAVES can decrease sound level up to 25 dB due to sound mode coupling in an exact frequency.2- INTERNAL WAVES can focus and defocus sound WAVES because of sound speed fluctuation. The purpose of this study is a laboratory investigation of INTERNAL WAVES caused by oscillation of a cylinder in a stratified glass channel with 3 meters long, 0.5 meter width and 1 meter height, on the sound WAVES propagation. In this study, using the double bucket and filling box method for generating stratification that is measured by one pair of salinity and temperature meters fixed on a rail that can move up and down. Using the usual methods of setting up INTERNAL WAVES and using acoustical transducers in 53 kHz frequency, INTERNAL wave's effects on the propagation of sound WAVES, were investigated. In this study with usual optical method (Synthetic Schlieren) the INTERNAL WAVES generated in the tank can be detected. In this method INTERNAL wave generated in the glass tank change optical index of water layers and cased deviation of the image straight lines designed on the back of tank. Laboratory results showed that sound WAVES can be focused and defocused due to the normal modes of INTERNAL WAVES. Some 9 experiments were done mainly in cases with vertical linear density stratified fluid. As the modal structure of INTERNAL WAVES in the water tank change due to the WAVES, constant density surfaces change slopes, hence changing the sound ray's paths and the amount of signals reaching the receivers. Similar results of numerical simulation also show similar behavior in the strength of the acoustic signal. The numerical simulation were done by AcTUP v2.2L software that use KERAKENC method based on normal mode method. The acoustic signal can be weakened up to 54 per cent depending on the degree of sound ray divergence. We can conclude that in the laboratory tank in this study INTERNAL WAVES can affect the sound WAVES by focusing and defocusing and not by mode coupling. Similar behaviors can be expected in the open ocean as the existence of INTERNAL WAVES is ubiquitous. For this goal dimensionless numbers should be use. Bowen (1993) showed that for simulating a sound WAVES interaction with a phenomenon in laboratory scale we can use ka=k' a'. With this formula we can compare laboratory results with real results in oceans.

INTERNAL WAVES (IWs) are oscillations of the water column that occur at the interface ‎between two layers of different densities. They play an important role in ocean ‎dynamics, mixing, and biogeochemical processes. However, IWs are difficult to ‎observe and measure in situ, especially in complex and narrow regions such as the ‎Strait of Hormuz. This study uses bathymetric data and over 100 satellite and radar ‎images from different sensors and platforms to investigate the occurrence and ‎behavior of IWs in the Strait of Hormuz. The results show that IWs are persistent in ‎this area due to the interaction of the INTERNAL current with the steep slope of the strait. ‎The WAVES emerge in shallow waters near the coasts of Iran and Oman, but they ‎change their direction and location when they reach the continental shelf. The leading ‎crest of IWs has a length ranging from 10 to 20 km, and the wavelength varies from 1 ‎to 3 km. The study confirms the findings of previous numerical simulations of ‎INTERNAL wave generation and propagation in this region. It also suggests that the ‎bathymetry is the main factor influencing IWs in the Strait of Hormuz, rather than ‎water column stratification. This study provides new insights into the spatial and ‎temporal characteristics of IWs in the Strait of Hormuz, which can help improve the ‎understanding and modeling of ocean circulation and ecology in this region‎.

The INTERNAL WAVES complicate the propagation process of sound in the water.These WAVES are considered the main cause of disturbances in sound speed, and now it is known that the INTERNAL WAVES are the dominant parameter in the change process of sea frequency spectrum, as these changes range from many hourly cycles (floating frequency) to almost one daily cycle (inertia frequency).The profile of mass sound speed in shallow waters depends on salinity and temperature gradients in turbulence INTERNAL WAVES. Here, the assumption is that the only probability function source is the turbulence INTERNAL WAVES in a water column. This investigation aims to use the mathematical models to study the INTERNAL wave effects on propagation of sound WAVES in shallow waters and that the WAVES how affect the sound propagation and depend on what parameters? We used the data gathered from Persian Gulf to calculate the parameters such as: sound speed, floating frequency, the ratio of resulted turbulences in sound propagation by vertical movement, phase functions and INTERNAL wave domain. Meantime, based on a given wave length (in the study area: 235 m.), the shape of first mode has been compared to the other modes.The probability density functions have been calculated for two different modes.Comparing the ratio of generated turbulences in sound propagation by vertical movement and horizontal speed of particle, showed the horizontal movement is considerably less than the vertical one and also by increasing the depth (consequently decreasing the floating frequency), vertical movement is raised highly. The highest floating frequency and turbulences generated in sound propagation by vertical movement are found on the places near the water level and this is due to thermocline existence and on the other hand in the same places we have the lowest range of vertical movement.

The wake and INTERNAL WAVES of a moving three dimensional (3D) airfoil body in a stratified fluid has been investigated in a large stratified tank with a finite depth using movies of shadowgraphs of the flow fields.Typical Reynolds and Froude numbers of the flow varied between 103 and 104, and 0.3 and 2 respectively.The flows are generated often by towing the body in a uniformly stratified flow, while limited cases are carried out with body stationary and the channel was in recirculating mode. For some experiments the density profile had a stepped like shape. The wake flow is often consisted of INTERNAL WAVES including random and coherent ones. Distortion of density fields was also observed ahead and above the body in cases where the Froude number was subcritical. Results show that as the Froude number (Fr=U/Nh, where U is the body relative velocity, N is buoyancy frequency and h is the thickness of the body) is increased, the flow undergoes from a subcritical narrow wake (for Fr<1) to an INTERNAL WAVES dominated flow (for Fr~1) and then to a hydraulic jump with a turbulent wake with some mixing (for Fr>1). Typical wavelength of the exited INTERNAL WAVES is increased with Fr, as the theory predicts. The wake of the flow for Fr>1.4 appeared to collapse and some INTERNAL WAVES emission from it could be observed. Usually two types of INTERNAL WAVES, namely random small scale and large scale, more regular WAVES are observed.

Sound is one of the forms of mechanical energy and the two main characteristics of sound are intensity or power and frequency or wavelength of sound.their performance against the incoming sound wave, industrial silencers can be divided into two general groups of resonating and absorption silencers, the main difference between these silencers is the release of sound energy from the channeling system, which is one of the common examples of the use of resonating type silencers, their use in It is the INTERNAL combustion engines that distinguish absorption silencers from the resonator type based on the fact that the main and visible part of the act of muting the sound is achieved by changing sound energy to heat energy.The goal of this article is to design a muffler based on the breaking of sound frequencies resulting from the movement of fluid in the exhaust output of vehicles, which leads to a reduction of at least 50 db of sound and gives the operator enough peace and concentration. In this article, after examining three types of mufflers, absorbent mufflers that use the properties of porous absorbent material to absorb passing sound and are the simplest form of mufflers, have been selected, analyzed and reviewed and are suitable for the OM457 engine of Idem Industrial Company. It designed for maximum inlet exhaust temperature is 520 and for the maximum kW power is 315 with the maximum discharge relative pressure of 185 mbar for homogenization with the standard atmosphere.

In this research we investigate the role of normal modes of INTERNAL WAVES in generation of layered structure in a part of Persian Gulf where river plume inters, and in some laboratory experiments. The model prediction and observations show that layers so formed have a thickness of about 2m based on salinity variations with depth, but layers (about 5m) based on horizontal velocity profiles. Laboratory experiments with a plume outflow in a "filling box" profile also generate normal mode layered structure with where is layer thickness and is the plume depth. In these experiments the of the flow is smaller than the of field flow; hence, the normal modes are substantially dissipated with depth. The comparison between the field study and the experimental observation shows that the two are, within the experimental limitations, in agreement.It should be emphasized that field observation is for semi-enclosed seas but the laboratory experiments are for enclosed region. Hence some of the discrepancies in the results of two cases are inevitable.

A B S T R A C T Temperature is one of the climate elements that has fluctuated a lot over time. When these fluctuations increase and decrease more than normal and are placed in the upper and lower regions of the statistical distribution, if continued, it can lead to the creation of heating and cooling WAVES. The purpose of this study is to analyze the temporal and spatial changes in heating and cooling WAVES in Iran during a period of 50 years. For this purpose, the temperature of 663 synoptic stations from 1962 to 2004 was obtained from the Esfazari database. Then, in order to complete this database, the daily temperature from 2004 to 2011 was obtained from the Meteorological Organization of the country and added to the aforementioned database. In order to perform calculations and draw maps, Matlab, grads and Surfer software have been used. The results of this study showed that the index of cooling WAVES and heating WAVES, while having a direct effect on each other, had an increasing trend in most of the area of Iran. The statistical distribution of the index of cooling WAVES is more heterogeneous than that of the index of heating WAVES. So that the spatial variation coefficient for cold WAVES is 84.22%. Also, the index of cooling WAVES has more spatial variability. The highest common diffraction of the index of heating and cooling WAVES has been seen in the northwest, east and along the Zagros mountains. Analysis of the indexes trends show that heat WAVES have intensified in 65.8% of Iran and the intensity of cold WAVES has decreased in 48.5% of Iran Extended Abstract Introduction Temperature is one of the major climatic variables, which it has a direct impact on different aspects of human life. It plays an essential role in the growth of crops and is considered a key driver of the biological system(Reicosky et al, 1988). It is associated with several types of extremes, for example, heat and cold WAVES which caused human societies maximum damage. Past occurrences of heat WAVES hitherto had significant impacts on several aspects of society. Have increased Mortality and morbidity. Ecosystems can be affected, as well as increased pressure on infrastructures that support society, such as water, transportation, and energy(Dewce, 2016). The long-term change of extreme temperatures has a key role in climatic change. The form of statistical distribution and the variability of mean values and also extreme event indicate a change in the region. It can be a small relative change in the mean as a result of a large change in the probability of extreme occurrence. Also, the variation in temperature data variance is significantly more important than the mean, for assessing the extreme occurrence of climate(Toreti and Desiato, 2008). The average surface temperature has increased the world between 0.56 and 0.92 ° C over the past 100 years(IPCC, 2007). Meanwhile, it was in the Middle East, the average daily temperature increased by 0.4-0.5 ° C in decades(Kostopoulou et al, 2014; Tanarhte et al, 2012). Considering that not many studies have been done in the field of spatio-temporal Variations of the heating and cooling WAVES thresholds in Iran, in this study, the spatio-temporal Variations of the heating and cooling WAVES thresholds in Iran during 50 years were examined and analyzed.   Methodology The daily temperature from the beginning of the year 21/03/1967 to 19/05/2005 was obtained from the Esfazari database prepared by Dr. Masoudian at the University of Isfahan. In order to increase the time resolution of the mentioned database, the daily temperature of observations from 05/21/2005 to 05/12/2012 has been added to the mentioned database using the same method, and the exact spatial resolution (15 x 15 km) is used as a database. Threshold indices of heating WAVES are the average numbers between the 95th and 99th percentiles, that is, the extreme hot threshold to the limit of excessively extreme hot. For extreme cool, from the 5th percentile down to zero is used. Of course, a condition was added to these thresholds, which is that these thresholds must be repeated two days in a row. These thresholds were extracted for each day in the 50 years of the study period and used as the original database. In order to analyze the relationship between cooling and heating WAVES, Pearson's correlation coefficient was used and regression was used to analyze the trend.   Results and discussion The average of cold WAVES was 5.26 ° C and for the heat WAVES is 30.20° C. Generally, if the temperature is upper or lower than this threshold, it is considered as hot or cold temperatures. A comparison of the median, mode, and average of cold WAVES with heat WAVES shows that the distribution is more heterogeneous for cold WAVES and its CV is 84.22%. In southern Iran, the average threshold heat WAVES are higher. This situation can be caused by the effects of subtropical high-pressure radiation, low latitude, and proximity to the sea. Though the threshold is higher in these areas, fewer fluctuations and changes are seen in the area. Heights moderate the temperature so they pose a minimum threshold for heat WAVES i.e. an iso-threshold of 25 ° C is consistent along the Zagros mountain chains, but in the west and east of Zagros Mountains, the threshold of heat WAVES is increased. Heat WAVES have increased in most areas of the country. So nearly 85 percent of the Iran has been an increasing trend, of which 65.8 percent is statistically significant at the 95% confidence level. Still, more areas of the country (60 percent) have a trend between 0.00828 and 0.00161. As can be seen, only 15% of the land area (including the southwest and northwest of the Country) had decreased heat WAVES. Cold WAVES, in most parts of the country, have a Positive Trend. However, about 25 percent of the study area's cold WAVES have a negative trend. they are located in areas higher than Latitude 30°. The largest decline of the wave's trend along the country is highlands. Nowadays, most of the country, has a trend between 0.01494 and 0.00828 ° C, respectively. Conclusion Common changes and effects of heat and cold WAVES had a direct relationship in many parts of the country. It is remarkable common variance in the East reached 55 percent, according to statistical significance. In some areas of the northwest and southwest, which have been impressive heights, the common variance is 40 percent. This common variance in mountains area has been high values. Investigation of heat WAVES trend shows that 65.8% of Iran significant positive trend and 7.1% significant negative trend. Also, the cold WAVES trend has indicated a 48.5% significant positive trend and a 10.8% significant negative trend. Climate change and global warming have changed the frequency and severity of temperature extremes. The present study, by examining the number of warm WAVES, concluded that the warm WAVES have increased in magnitude in 65.8% of the Iran zone. Also, the study of the cold WAVES trend showed that 48.5 percent of Iran had a positive trend, which means that the amount of temperature in the cold WAVES increased In other words, the severity of the cold has been reduced And only 10.8 percent of Iran had a negative cold wave trend And it shows the intensity of these WAVES is reduced.   Funding There is no funding support.   Authors’ Contribution The authors contributed equally to the conceptualization and writing of the article. All of the authors approthe contenttent of the manuscript and agreed on all aspects of the work declaration of competing interest none.   Conflict of Interest The authors declared no conflict of interest.   Acknowledgments  We are grateful to all the scientific consultants of this paper.