اسماعیل ولیزاده

Gel propellants are promising in the aerospace industry due to the benefits of both solid and liquid propellants. Unlike their base liquid propellants, the gel propellants have a non-Newtonian behavior that complicates their behavior in the propulsion system, especially in the atomization process. In this paper, the internal flow of a pressurized swirl injector for gel propulsion was studied using computational fluid dynamics based on the power law model. The simulations were performed in 3D mode and based on the volume of fluid model (VOF) in different values of the consistency and flow index of the fluid behavior at a constant inlet flow rate. The results showed that by increasing the value of fluid flow behavior index (n), the required pressure decreases for a same mass flow rate. The required pressures of the fluid flow of 0.063 kg /s were obtained as 1.8 and 0.45 MP for n = 0.2 and n = 0.6 respectively. The results also showed that increasing the consistency index, in terms of flow pattern, has the greatest impact on the injector swirl chamber so that the length of the air core formed along the injector axis decreases with increasing the conformity index.

Gel propellants are the optimal state of liquid propellants. Gel propellants not only have the advantages of liquid and solid propellants, but also don’t have the disadvantages of the mentioned propellants. The rheological properties of these propellants have a great effect on their propulsion systems, especially in the dynamic state. Regarding the fact that missile and rocket propellants are usually toxic and it is very difficult to study their dynamic behavior in the propulsion system, in this study to select a gel simulant (non-toxic) that can simulate the dynamic behavior of the UDMH gel fuel sample, different gel simulants with methylcellulose, carboxymethyl cellulose and hdyroxypropyl methylcellulose were made and the dynamic behavior of the gel simulants were compared with the dynamic behavior of the UDMH gel fuel. The results showed that the gel simulant made with 0.85% wt. of HPMC gellant is very similar to UDMH gel in terms of dynamic behavior. Also, among rheological models power-law, cross, carreau-bird, and carreau-yasuda, the carreau-yasuda rheological model was able to predict the behavior of the selected gel simulant in a dynamic state in a wide range of the shear rates.

The Gelled propellants have a promising future for aerospace applications because of possessing the advantages of both solid and liquid propellants. A gel propellant is a liquid propellant whose rheological properties have changed by the addition of gellant and other additives. The rheological properties of the propellant have a significant influence on the atomization process. In this paper, the rheological properties of the gel propellant are introduced. Then, the effect of gel propellant properties on the atomization in the swirl injector has been investigated. Subsequently, some important points for designing a swirl injector that can influence enhancing the atomization quality of the gelled propellant are presented. The results of the studies revealed that higher initial viscosity of the gelled propellant compared with the mother liquid propellant cause increase in the discharge coefficient, the size of droplet diameter, and the breakup length of the gel sheet while causing a decrease of spray cone angle in the swirl injector compared with liquid propellant and in the point of view of influenced by the size of droplet diameter on the gel propulsion system. Considering the shear thinning effect of the gel propellant and ability to atomization of gelled propellant by swirl injector, to improve the quality of the atomization of gel propellant, the design of the swirl injector should be such that the shear rate applied on the gel propellant should be increased to conquer the initial viscosity of the gel.

Climate change and global warming are the greatest challenges that humanities have ever faced. Temperature variations, quantity and pattern of precipitation are the important potential impacts of climate change which may affect water resources and drought conditions. Mann-Kendall trend test and Pttitt homogeneous test were respectively used to detect trend variation and abrupt changes in the time series.The SPEI drought index which is based on precipitation and temperature data, is not only designed in a way to consider both precipitation and potential evapotranspiration (PET) but also has the capacity to include the effects of temperature variability on drought assessment. Therefore, the objet of this study is to investigate the trend and the detection of change points in seasonal series of SPEI drought index in Iran, and for this purpose the non-parametric Mann-Kendall and Pettitt statistical tests has been used. In the first step, the SPEI data, calculated based on monthly rainfall and evapotranspiration is extracted from those parts of the SPEI world database covering Iran, and are about 624 points of the 0.5° geographic network were separated from the entire data and stored in the Excel format. Then, the 50 years seasonal times series of SPEI data during the period of 1969-2018 were made for different seasons of the year. Finally, the nonparametric Mann-Kendall trend and Pettitt change point detection tests were performed on the data, and the results were analyzed. The results of using the Pettitt test in 624 points from Iran showed that in between the series of SPEI drought index in the spring, summer, autumn, and winter, 11, 31, 8, and 15 percent of points had significant change point, respectively, and their spatial location are the decreasing change points in the eastern and north-west in spring, northernwest, northern east, middle part and southern east in winter. Meanwhile in summer and autumn seasons the increasing and decreasing change points are in dispersed points from the southwest, and the south and northeast and the increasing change points in the middle parts of Iran, and parts of the south and north of the country, respectively. Also, the results of using Mann-kendall test showed a significant decreasing trend in 28 percent of points for spring, a significant increasing and decreasing trend in 5 and 25 percent of points for the summer season, a significant decreasing trend in 18 percent of points for the autumn, and also the existence of significant increasing and decreasing trends is in 1 and 15 percent of points, respectively in winter. The spatial location of these points for the four studied seasons was in the east, northwest and south of the country, half east, southwest and scattered parts from the south of the country, the central parts of the country, as well as the northeast and northwest, respectively. Result of using Mann-Kendall and Pettitt statistical tests indicated that climate change has occurred in parts of the country, varies from one season to another in such a way that in east and northwest parts of the country in spring and in north-west and south-east parts of the country in winter, more dry conditions are visible but in autumn, more humid condition were observed in central parts of the country. According to the fact that most of the country's precipitation is in winter and spring, this drying trend will cause a hazard in reducing water resources. The results also indicate that in most of the cases that a change-point exist in the drought index, a trend is also observed in data series based on Mann-Kendall trend test.

In designation process of liquid rocket engine, selection of cooling rout of thrust chamber have important role for assessing safety and reliability of the engine. Also the correct perception of internal flow characteristics in LRE thrust chamber, such as temperature and pressure, plays effective role in optimization of engine design to decrease consumption fuel and how to cooling the thrust chamber wall. One of the ways to cooling the thrust chamber wall to decrease the combustion temperature near the wall is injection extra fuel in this section. In this paper, numerical investigation of the effect of film cooling with mixed heat transfer on decrease the thrust chamber wall temperature in the LRE, relative to condition that only exist mixed heat transfer in the wall was performed.

Declining condition of water resources cannot be shown by single-variable drought indices because of changes in precipitation and temperature due to climate change. Accordingly, multivariate drought indices are considered such as the Standardized Precipitation-Evapotranspiration Index (SPEI). In order to study the trend of changes in the severity of meteorological drought in the geographical zone of Iran, the SPEI global network data was used over a 30-year statistical period, and trend detection test and Sen's slope estimator were performed on their seasonal series. Then, their results were mapped in the GIS and the results showed that the highest drought trend is in the winter between seasons, and more than 94 percent of the country's area shows a declining slope in the drought index time series. The trend of this slope in the west and north-east of the country is statistically significant. Also, the eastern half of the country shows a drought trend in the summer, but a better situation prevailing in Iran in spring and autumn, and a small percentage of the country's area indicates a significant drought trend. So that in the spring and autumn, the slope of the trend line in 85 and 91 percent of the country is less than and equal to 2 percent, respectively. Generally speaking, the result of the Standardized Precipitation-Evapotranspiration Index showed that climatic changes are occurred in Iran and the country is going towards more dry periods in future years.

In the present study, the low frequency combustion instability using lag time Szuch and Wenzel has been investigated. For the analysis effect of evaporation on combustion instability from lag time the fuel and oxidizers is used, so that Stability boundaries of performances engine is obtained. in the combustion chamber each of processes of atomization, evaporation, mixing and ignition have a lag time for themselves, In the meantime, the evaporation lag time is dominant and therefore as combustion controller process be considered. In the result with this assumption, the time of evaporation that previous stage was obtained to enter drop evaporation equations into and with the use of the equations for energy and mass preservation and transfer of Mass and heat has been analysis. So in the end the ITC model has been used and we can to calculate the drop diameter in the specific evaporation time. To do this, the software is provided. According to calculations, To lag time evaporation of 1.4 milliseconds, diameter drops 123.4 micron for normal heptane has been obtained.

This study is a try to design a spike nozzle and simulate its flow-field in different conditions. Hence, spike nozzle design methods were studied and accordingly the design code was developed. Then the behavior of flow in this type of nozzle was simulated numerically by means of computational fluid dynamics. In order to conduct the simulations, four turbulence models suitable for solving the flow-field of spike nozzle were used, not only to model the performance of the nozzle in design and off-design conditions, but also to identify the best model for the accuracy of the solutions. To ensure the accuracy of the simulations, numerical results and experimental data were compared. It was found that applied models in case of using high quality grids with proper dimension near the nozzle walls, can predict the nozzle flow pattern with acceptable approximation. Also the comparisons revealed that the amount of pressure on the spike wall calculated by Realizable k-ε model, is generally identical with experimental results and in the worst condition the difference between them is 15%, so this model has the best agreement with experimental results. Besides, comparison of taken photos during experiments and extracted contours from numerical analysis, shows the high ability of applied numerical method to predict spike nozzle flow-field. Therefor it can be claimed that by using the proposed method in this research, there is no need to perform cold-flow tests during the design and construction of spike nozzles.

Estimating soil moisture along a vast area is mostly expensive and sometimes undoable. One of the newly available technique is remote sensing, which allows the possible surface soil moisture estimates in a large scale. Therefore, the objective of this research was to investigate the possibility of estimating surface soil moisture using MODIS satellite images in compare to soil moisture measured data. To conduct this research, vegetation and temperature indices from MODIS images were extracted from October 2013 to June 2014 period for Gonbad-e Qavus region, then measurements were calibrated with field measurement data. The results indicated that significant but weak correlations are available between NDVI and NMDI indices with measured surface soil moistures (R= 0.62), while there were highly significant, but negative correlations (p ≤ 0.01; R = -0.89) for LST index and thermal bands of 31 and 32 with surface soil moistures. The TVDI index also had highly significant, but negative correlation (p ≤ 0.01; R = -0.90) with surface soil moisture. There were also highly significant linear and exponential correlations between SWI index and surface soil moisture. In conclusion, the results indicate promising relations for thermal and combined models to estimate surface soil moisture relative to vegetation models.

Vortex combustion chamber which is a new generation of liquid fuel engine with different arrangements of injectors generated a vortex flow into the combustion chamber. This vortex contributed to increased cooling and mixing the components of the propellant in the combustion chamber and can be generated a complete combustion in a small volume chamber. In this chamber several type of injector used in various locations including, centrifugal, flow and vortex injectors. In this study, the design of these injectors and then experimental test to investigate the effect of geometrical parameters on their hydrodynamic characteristics is done using water flow. Spry forming process, flow measurement, pressure drop and injector spray angle including hydrodynamic characteristics that have been studied. The results show acceptable agreement of the predicted design with performance of injectors. Accordingly, centrifugal and flow injectors that injected the fuel and oxidizer into the chamber were selected and shown that increasing the number of tangential vortex injectors to 6, generated more uniformity in the rising vortex flow in the chamber but the entry angle to 5 degrees no significant effect on rising flow.

The ongoing developmental studies on the application of subscale liquid rocket engines as small thruster and laboratory tester are briefly reviewed. Then a detailed design & manufacturing process of a laboratory liquid subscale engine with single swirl double base injector of 300 N thrust for this reaserch is presented. For the preparation of pressurized water, fuel and oxide, a test facility has been prepared. Results of water analogy tests are presented. Initial firings using the real fuel and oxide were not successful. Low fuel flow, low mixing area of the fuel and oxide, and contamination in the TR-1 were considered to be the reasons. Overcoming to these problems resulted in successful firing of the subscale engine. obtained results were adapted to design expected results.

Vortex combustion chamber is the new generation of liquid propellant engines chamber, where with the help of different arrangement of injectors, an inner combustion chamber vortex flow is created. This vortex can extremely help cooling and increasing the amount of propellant components mixing in the combustion chamber so it makes it possible to create a complete combustion in a low- capacity chamber. In this research, a vortex chamber has been designed and manufactured for carrying out cold tests with water as its working fluid, in order to study impact of different parameters, including pressure drop, injector quantity and input angle, chamber diameter and the thickness of the supporting step, on the performance of this type of chambers. The designed chamber, has a great deal of capabilities such as replacement ease, change in pressure drop and injectors’ input angle and studying different supporting step’s thickness to create vortex flow. Since practical investigation of all parameters is not cost-effective, cold test has been conducted for some samples and both simulation and validation have been done for it. The simulation results and chamber performance in the tests could match very well; therefore as a result of simulation assurance, the processes and other parameters in the chamber could be studied. By doing these tests we can move toward design, manufacture and test of the main vortex combustion chamber.

Studying the phenomenon of frost and chilling is one of the fundamental researches in the field of Agroclimatelogy and knowing how and when they occur, could be useful significantly in the agricultural sector. Climate change which causes changes in temperature parameters influences the frost. To this end, a research was done so that the beginning of the first frost and chilling in autumn, the last frost and chilling in spring and also period of the frost and freezing at three weather stations in Tabriz, Qazvin and Mashhad would be checked during 1961-2005 as the basis period and during 2005-2050 as the future period. The data of the future period was produced based on output of Hadcm3, under the scenario A1B, using the software of data generator LASR-WG. Then time series of the dates of the first and last frost and chilling in autumn and spring was formed for each year during the periods of the study and the best statistic distribution was fitted for each of them and the possibilities of their happening were calculated. The results showed that at all stations affected by the climate change, the first frost and chilling in autumn will occur earlier and the last frost and chilling in spring will occur earlier and length of frost and chilling period will decrease.

The manner of spray the fuel has an important effect on stability and convenient mixture of fuel and oxidizer. Swirl injectors because of formation of uniform spray cone and proper distribution of the fuel have been used in many rocket engines at aerospace industries. Formation and development of air core in the interior stream of swirl injectors and simulation of them is complicated. Double base-swirl injectors have better atomization and have more effective and uniform mixture and combustion. Inner stream has an important effect on spray characteristics. In this article we want to simulate liquid film، air core and spray angle in double base swirl injector. Inner stream of swirl injector simulate with two-phase method and we use air for gas-phase and water for liquid-phase and validate our results with experimental results. Because this way is very cheaper and faster rather than experimental studies.

The main of aim present study was identifying of high intensity of gastrointestinal parasitic worm infestation in sheep in the Abhar city. Planning was done with taking samples from sheep Abhar city livestock during early winter 2009 to late autumn 2010. Fecal samples were tested using Flotation and Sedimentation diagnostic method. In order to investigate the relationship between age, sex and season of sampling square test was used. In this study, 1600 sheep were studied and fecal samples were obtained of these animals. All of examined animals were treated at least one time by antiparasitic drugs. Results indicate contamination 542 (33.87%) of studied sheep were infestation to gastrointestinal parasitic worms. In some of these cases, combined different parasitic infestation was observed and at all 614 cases were found positive. Of these, 216 cases (13.5%) were infested to the digestive Ostrongylus, 99 cases (6.18%) to Marshallagia, 88 cases (5.5%) to Nematodirus, 63 (3.93%) were infested to the Trishuris. Infestation to Monezia. Spp were observed in 41 (2.56%) and Fasciola infestation in 58 cases (3.62%) and Dicrocelium in 49 cases (3.06%) of studied animals. According to the results obtained digestive Ostrongylus highest incidence of infestation related to the digestive and the lowest incidence of associated species was Monezia.Spp.. Regarding the reported contamination of all parasites in the mid and late spring and reached its peak in the mid-autumn peak shows slight. On statistical analysis significant correlation between the severity of infection with parasites with sex, age, month and season of sampling was not observed (P>0/05). But significant difference between contamination and the different seasons of year and different month was found (P 0/05).

An investigation was conducted in order to determine the tick species of sheep body surface and their seasonal population variations in maraghe province from march 2008 to april 2009. Sampling was done from overally 1200 sheep of both sexes. Collected data were analyzed using SPSS computer software. the results revealed that 266 (22.22%) sheep was infested by hard ticks. the highest percentage of the sheep ticks infestation was observed in june 2008, while lowest percentage was in during February 2008. There was a significant difference (p<0.05)in the tick population of sheep during the seasons and months of the year.Out of 1279 ticks were collected on sheep and were identified as: R.turanicus (48.51%), Hy.anatolicum. anatolicum(15.01%), D.marginatus (11.91%), R.sanguineus (8.22%), Ha.punctata (4.32%), Ha.sulcata (3.66%), Hy.anatoliium.excavatum (3.22%), Hy.marginatum (2.56%), R.bursa (2.53%). the difference of ticks site preference was significantly noticeable.Distribution of ticks over different parts of sheep body surface according to their frequency were as follow respectively:head and meck(63%),under the tail(23%), under armful(10%), groin(4%).(p<0/05)

In order to determine the tick specie of goats, reared in cities of west-Azarbaijan province, the present investigation was performed from March 2006 (Farvardin 1385) to April 2007 (Esfand 1385). Meanwhile, distribution of ticks according to age and sex on different part of the body and the seasonal variation of tick population and infestation were also studied. Overall 1800 goats of both sexes, from 21 cities and their suburbs in west-Azarbaijan province were examined for tick infestation. The results revealed 52 (2.88%) goats were infested by hard ticks. The highest percentage of infestation was observed in Miandoab area during June 2006 (Khordad1385), while the lowest percentage was in Shahindegh area during February 2006. There was a significant difference (p