Density separation has many applications in metallurgy, medicine, clinical chemistry, microbiology, and agriculture. This study investigates the factors' effects on density separation in order to benefit from this technique. The separation quality depends on the velocity of particles because as the velocity of particles increases, the mean separation needs less time so it gives better separation, so the parameter effect on the value of the velocity is studied. These parameters were volume fractions, the diameter of the sphere, the density of the sphere, and the viscosity of the fluid. Each parameter was studied by calculating the velocity of particles using Stokes' law. The velocity of particles is directly proportional to some properties of particles. These properties are the diameter and density of a particle because as these properties increase, the mass of particles increases, which leads to increased kinetic energy, which increases turbulence. Turblance's velocity is increasing. The volume fraction of spheres is another property of particles' effects on density separation. This parameter is inversely proportional to velocity because a collision between particles increases, which decreases turbulence. Fluid properties also have an impact on density separation. This property is viscosity. Its effect deteriorates the efficiency of separation because viscosity is the resistance of the fluid to flow that serves to displace the particle, which leads to a reduction in the velocity of the particle. The maximum separation happens when the sink and float particles separate at the same time. That happens when the sink and float particles have the same velocity in the opposite direction. That means when the sum of velocities equals zero. In this research, the maximum separation was derived when the sum of velocities equaled zero.
The impact resistances of concrete slabs have a different volume fraction replacement of waste plastic aggregate has been examined in this study as a fine aggregate as: 0% (reference), 10%, 20% and 30%. These tests include the splitting tensile, density, compressive strength. Also, the (ultrasonic pulse velocity tests) was carried out. Repeated falling mass was used in order to carry out the low-velocity impact test in which a 1300 gm steel ball was utilized. From a height of 2400mm, the ball falls freely on concrete panels of (500×500×50 mm) with a network of waste plastic aggregate. As per the results, a prominent development was seen in the mechanical properties for mixes involving polyethylene aggregate up to 20% as compared to the reference mix. A significant development was seen in low-velocity impact resistance of all mixes involving waste plastic fine aggregate as compared to reference mix. As per the results, the greater impact resistance at failure is offered by the mix with (20%) waste plastic aggregate by volume of sand than others. The reference mix increased by (712.5%).
This research project focused on examining and (rehabilitation) redesigning water networks in a city using the GIS-EPANET program in hydraulic network analysis. Due to the availability of outline data about the study area from the municipality's water distribution system (WDS), this study dealt with four cases. From a statistical calculation, the last case was best optimized, which resulted in a high pressure and an acceptable velocity as a result of high mean pressure (13.58) m, logical mean velocity (0.43) m/s, and accurate standard deviations of 1.214 and 0.48 for pressure and velocity, respectively. The study found that the network had a shortfall in pressure, estimated at 40%, due to the lack of expansion to accommodate the growing population. However, after conducting the analysis and identifying the problem, it was found that all regions were receiving adequate amounts of water. Nevertheless, the water speed in the pipelines throughout the network was deficient, below the recommended rate, with a minimum velocity of 0.02 m/s in the pipe (p3) but a minimum pressure of 7.02 m at the junction (607), indicating that the network design was ineffective. Comparing the results obtained with the real-world situation, it was discovered that the network has many violations and disruptions, causing water loss and resulting in low pressure reaching the customers. While the study found that the pressure inside the network was within acceptable modeling limits of (7–12) m, there was a reduction in the pressure charge due to the frequent use of water pumps inside the houses, especially as the circulated area was pumped further away. The error between the model and the real problem may be attributed to water leaks and disruptions from trees, gardens, landscaping, and livestock grazing, as well as the absence of a counter to calculate the water discharge volume to consumers
This research investigates the impact resistace of reinforced high strength concrete slabs with steel meshes (BRC) modified by styrene butadiene rubber (SBR) with different weight ratios of polymer to cement as follows: 3%, 5% and 7%. Reference mix was produced for comparison of results. For all selected mixes, cubes (100×100×100mm) were made for compressive strength test at (365) days. In conducting low-velocity impact test, method of repeated falling mass was used: 1400gm steel ball falling freely from height of 2400mm on reinforced panels of (50×50×800 mm) reinforced with one layer of (BRC). The number of blows causing first crack and final perforation (failure) were calculated, according to the former results, the energy of each case was found. Results showed an improvement in compressive strength of polymer modified high strength concrete (PMHSC) over reference mix; the maximum increase being of it were (3.93%-11.96%) at age of (365) days. There is significant improvement in low-velocity impact resistance of all polymer modified mixes over reference mix. Results illustrated that polymer modified mix of (3%) give the its higher impact resistance than others, the increase of its impact resistance at failure over reference mix was (154.76%) while, for polymer modified mix (5%) it was (30.95%) and it was (14.28%) for polymer modified mix of (7%).
The purpose of this paper is to developing a mathematical relationship between the Ultrasonic Pulse Velocity (UPV) and the compressive strength for concrete specimens subjected to different amounts of exposure of sulfate attack. The experimental data were collected from a research work by the author using concrete subjected to sulfate exposure and form a literature used an extensive concrete work without sulfate exposure. The sulfate exposures studied were 0%, 3%, and 6% of fine aggregate. It is found that with the same amount of sulfate exposure a clear relationship curve can be drawn to describe the UPV and compressive strength. This paper proposes the UPV-strength mathematical expression suitable for prediction of the concrete strengths when subjected to sulfate attack.
This study aims to improve different properties of sustainable self-compacting concrete SCC containing treated and modified polyethylene terephthalate PET fibers. For this purpose, gamma ray surface treatment and geometric modification were utilized for the used PET fibers. Concrete fresh properties include slump flow, T500mm, L-box and sieve segregation while mechanical properties include compressive, split tensile strength, flexural strength, static modulus of elasticity and impact strength. Further, physical properties and related durability properties comprise dry density, ultrasonic pulse velocity, porosity and water absorption. The results obtained demonstrated that the treatment and the modification used for the PET fibers slightly reduced the fresh properties of produced sustainable SCC (slump flow, T500 mm, L-Box and sieve segregation). However, they were within the limits of the SCC specification as reported in EFNERC guidelines. Further, concrete hardened properties in terms of compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, impact strength, ultrasonic pulse velocity, decrease in the dry density, decrease in porosity and water absorption increased significantly.
Previous studies showed that fire incidents cause a considerable deterioration of limestone samples' engineering and physical properties. Various laboratory tests were used in previous studies to investigate the properties of limestone. These tests included destructive and non-destructive tests like the hammer test, ultrasonic pulse velocity test, water-capillary rise test, and water transfer properties test, as well as destructive tests like the unconfined compression test and Brazilian tensile test. The stones of buildings exposed to fire are occasionally assessed on the site. This study analysed the physical and mechanical changes that occurred to the limestone samples when subjected to high temperatures, the damage mechanism, and laboratory or field damage assessment. This study also includes a review of the most significant studies that looked at how alternative cooling techniques—rapid water cooling or gradual air cooling—affect stone samples subjected to high temperatures and compared the behaviour of the samples in each scenario
This search includes analysis of Fallujah water network that are fed from the old drinking water treatment station in Fallujah , which provides citizens in residential areas (AL-Jolan District, AL- Mu'tasim district, AL-Andalus district) by drinking water by using a program (EPANET) in the hydraulic network analysis .It was found their are lack in the required amount of water which estimated by about 20% due to oldness of the station and the lack of expansion by estimation the population growth the city. After input required the data in the analysis in got the results, it was noted that the three areas were getting the amount of required water, but the speed of water in the pipe network was very low and below the allowable limits (less than 1 m / s), this means that the design of the network has not takes into account the economic side and health status. The results were compared with the situated case and found a lack of water amount reaching the people as a result of trespasses and interruptions which occurring in the network, as well as the head pressure which reach the supply points fall within the permissible limits where ranging between (38-48 m) but the use of water pumps in homes lead to decrease the head pressure whenever the node far away from the drinking water station.
Recently, the investigations studies of simulating flow over spillways have increased using numerical models. Due to its important structure in the dams to pass flood wave to the downstream safely. Researches finding have shown that CFD (Computational fluid dynamics) models as the numerical method are a perfect alternative for laboratory tests. Performance analysis of the CFD platforms Ansys Fluent-2D and Flow-3D are presented, focus on finding the variations between the numerical results of the two programs to simulate the flow over ogee spillway. The present study treats the turbulence using RNG k-ε of RANS approach, and also use the Volume of Fluid (VOF) algorithm to track the water-air interaction. The Fluent-2D and Flow-3D accuracy are assessed by comparing representative flows variables (velocity; free surface profiles; pressure; and the turbulent kinetic energy). The results of both codes have been also compared with experimental data. The results of the analysis show an excellent agreement between the two platforms data, which could assist in the future by using both programs to calibrate each other, rather than traditionally relying on laboratory calibration models.
Natural convection heat transfer in two-dimensional region formed by constant heat flux horizontal flat tube concentrically located in cooled horizontal cylinder studied numerically. The model solved using the FLUENT CFD package. The numerical simulations covered a range of hydraulic radius ratio (5, 7.5, and 10) at orientation angles from (0o up to 90o). The results showed that the average Nusselt number increases with hydraulic radius ratio, orientation angles and Rayleigh number. As well as enhancement ratio for Nusselt number at orientation angle 90o and hydraulic radius ratio 7.5 equal 24.87%. Both the fluid flow and heat transfer characteristics for different cases are illustrated velocity vectors and temperature contours that obtained from the CFD code. The results for the average Nusselt numbers are compared with previous works and show good agreement.
Enhancing the hydrothermal performance of plate-fin microchannels heat sink (PFMCHS) promises smaller size and lighter weight, and then improve the heat removal in consequently increase the speed of electronic devices. In this numerical study, an innovative hydrothermal design of PFMCHS is suggested by inserting elliptic pins inside microchannels in different; aspect ratio (AR) of pin, pin number ratio (ψ) in order to optimize the hydrothermal design of this kind of heat sinks. The main objectives of this study are; investigating the effect of pins on the performance of PFMCHS by investigating the best geometry in the pinned-fin MCHS and which is higher, thermal or hydraulic performance of this kind of heat sinks and what is the optimal number of pins numerically and what about the pressure drop penalty in the proposed design, little, modest or high increase. It is seen that the thermal resistance of the pinned fin MCHS is about 50% lower, and pressure drop of it is much higher than that of the (PFMCHS) under the condition of equal wind velocity. Maximum mechanical fan power reduction obtained is about 57% for the pinned fin MCHS with ψ = 1 and Dh = 1 ×10-3 m compared to the corresponding original channel heat sink. To show the overall performance of the two parameters; aspect ratio (AR), pin number ratio (ψ), the overall JF factor is estimated and the concrete findings shows that the best hydrothermal performance is obtained at the greater aspect ratio which is around overall JF = 1.2. In addition, the trend of overall JF is going down with the pin number ratio, starting from 1.2 to 1.15. And the concrete findings show that pinned fin MCHS provides thermal performance of 1.42 times greater than the smooth one under the corresponding conditions when one pin is used in each channel
This paper presents the experimental results of composite slabs under static and impact loading. Total of six specimens classified one specimen test under static loading and the remaining five were tests under impact dynamic loading with different parameters as type of connections and degree of interaction of composite slab. Low - velocity impact test was adopted by select the falling mass (4 kg) made from steel material and formed as ball shape without nose. The ball dropped freely from height of (2.4 m) and strikes the top of composite slab. The designed dimensions of specimens is (500×500×60 mm) as reinforced concrete slab that reinforced by mesh of (RBC) and the steel plate is (3 mm) in thickness. Deflection due to first crack is recorded, number of blows caused first crack and failure were counted. The test results showed that the welded stud connectors gives high strength capacity and resistance under static and impact dynamic loadings than other than type of connections, also, full interaction as degree of interaction is better than others
The presented work investigates the effect of addition admixture (cement kiln dust) to concrete as a partial replacement of cement weight. Cement kiln dust was added by (10,30,50)% of cement weight.Four mixes were selected, three of them contain cement kiln dust (CKD) and one reference mix without any admixture for ages (7,28,90) days. Compressive strength ,flexural strength, ultra-sound velocity (UPV), slump, splitting tensile strength and static modulus of elasticity were tested.The test results indicated that the use of (CKD) led to significant decreasing in concrete strength in general and this decreasing increases with the increasing of (CKD), for example at 28 day the compressive strength of reference concrete (A) was 35 MPa, while the compressive strength of (B,C,D) contain (10,30,50)%CKD were (28,25,22) MPa respectively.
This research work includes study of sound insulation property of concrete samples with different densities. This study intended to present a proposed empirical formula to determine the sound insulation of concrete walls using the ultrasonic instrument. Experimental tests on concrete samples were made using the ultrasonic instrument, the sound insulation of concrete walls calculated according to a proposed empirical formula made in this work. This formula takes into consideration pulse velocity, wall width, and frequency .This formula is supported on a statistical criteria. The results are evaluated and compared with the values that computed using the most well-known formula, the comparison show compatibility of the results with tolerance of (3%).
This research, an attempt is carried to explain the use of new products of superplasticizers type (Glenium) locally recent period used in normal concrete strength,espeacailly in precast concrete. and the effect of medium hot weather climates on compressive strength of normal concrete made with various percentages of Glenium dosages , and to evaluate the dosages on workability of fresh concrete. Concrete mixes with two types containing of Glenium, G51 and G21. and different dosages of Gelnium, namely 0.8 and 1.2 liter per 100 kg of cement and reduction in water quantity about 25% Five mixes are made with 90 specimens, each mix contains 18 cubes ,half of specimens are cured by moist curing in normal condition, the other half of specimens are exposed to temperatures of 40oC.which is transferred to moist medium of hot water. The properties which are covered in this work consist of workability which represented by slump test, and strength represented by compressive strength and ultrasonic pulse velocity(UPV) tests. It is obtained that using the two types of Gelnium will improve the slump about (157% to 183%) compared with reference mix .The concrete cured at medium hot weather condition, show improves in compressive about (19.2 to38.12%) at 3 days age. The use Glenium type 51 is to be more suitable for normal concrete works in medium hot weather .
This study aims to investigate the durability properties and microstructural changes of self-compacting concrete (SCC) incorporating waste polyethylene terephthalate (PET) as fibers and as fine aggregate replacement. This is after exposed to saline environment (Alkalies, Sulphates, and Chlorides). PET effect into two forms was also evaluated for routine rheological properties of SCC and mechanical strength before and after exposure to sulphate salt. Five proportions of each form of PET incorporation in SCC mixtures were utilized. The volume fractions considered for PET as fibers were (0.25, 0.5, 0.75, 1.0, and 1.25)% by volume, with aspect ratio of 28%, and (2, 4, 6, 8, and 10)% by volume for fine aggregate replacements. Results indicated that the inclusion of PET adversely affected fresh propertis especially high proportions of PET as fine aggregate. Alkali silica reaction (ASR) outcomes illustrated an enhancement in the mix containing PET fibers, while fine-PET mix was slightly enhanced. Magnesium sulphate reduced mass and compressive strength of all mixes in percentages ranging from (0.18-0.90) % for mass loss and from (0.47-55.13) % for compressive strength loss. Ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity (Ed) increased due to the sulphate impact except for M0.5 and M10 which decreased in both tests. Chloride's theoretical and modelled results illustrated higher diffusion coefficients and lower surface chloride content of fiber-PET mixes as compared to fine-PET mixes. The predicted SCC cover depths for fiber-PET mixes were lower than those predicted for fine-PET mixes for 20 and 50 years of service life design.
A Numerical study has been conducted to clarify the effect of the buoyancy forces on the thermal development through a horizontal annulus sector heated with constant surface temperature. The study includes the solution of governing equations for the flow and heat transfer of different sections along the channel. Theoretically these governing equations were reduced to four, which are continuity equation, radial and tangential momentum equations, axial momentum equation and vorticity equation in which the variables were the temperature, vorticity, stream function and axial velocity. These equations were reduced to dimensionless equations in which Rayleigh, Prandtl and Reynolds numbers were presented. They were numerically solved by using the marching process explicit finite difference method and Gauss elimination technique. Numerical results for annulus sector heated by constant surface temperature for different values of Rayleigh numbers and total sector angles and diameters ratio were obtained and represented by stream function contours and isotherms and circumferential distribution of local Nusselt number. Also the results include the values of friction factor and average Nusselt number for the pure forced convection. Comparisons are made between the computed results and the analytical or numerical results available in the literature, for all cases compared, satisfactory agreement is obtained. The results include a survey of annulus sector surface in many sites of channel flow, whereas it is apparent that the buoyancy force causes the secondary flow to behave non uniformly at the entrance and then the average heat transfer will increase with the increasing both of diameter ratio and total annulus sector angles. A correlation relationship is extracted to find an average change of Nusselt after the stability of the flow in the fully developed region for the studied ranges of annulus sector angles and diameters ratio.
A new technique is presented by which lateral outflows of material , from an oblique impact collision between wax projectile and a rigid surface , are collected to form a high speed single jet. This jet has been shown to be capable of producing cavities in semi-infinite target of wax in a manner similar to that produced in a hypervelocity impact situation. The produced jet capability of penetration is found to be maximum at higher velocities of impact , lower values of standoff and with projectiles having angle of obliquity in the range (â=20-25o). A preliminary theoretical model is also presented in an attempt to describe the process of jet creation and jet characteristics. The present technique is proved to be promising in simulating penetration of semi-infinite targets by the impact of high speed jet .
This paper is aimed to study the effect of SiC addition as reinforcement to 6061 T6 alloy. Al 6061 T6 alloy SiC composites were prepared by melting the alloy in a vortex and adding 4 % and 10% weight fractions of SiC. Then pouring the mixture into a mould to obtain a bar of 12 mm diameter and 150 mm length. Wear specimens were manufactured in dimensions of 20mm x 10mm according to ASTM to the base alloy and the cast matrix alloy. Microstructure have been carried out to understand the nature of structure and Hardness test also implemented to specimens. Adhesive wear test have been conduct both on the alloy and composites at different parameters (time, load and velocity). From the obtained results, it was found that wear resistance improved during the carbide addition comparing with the base alloy as a result of SiC addition which contributed in improving the hardness of the alloy that reflects to the wear resistance and these properties were improved as the increasing of the carbide silicon percentage.