Transverse fuel injection in supersonic crossflow of scramjet combustors is one of the common methods for fuel-air mixing. Air jet injection before fuel jet can improve fuel penetration but with the excess stagnation pressure loss. In this paper, the position of air jet is changed to find the position that maximum fuel jet penetration height and minimum stagnation pressure loss is achieved. For numerical simulations, Two-dimensional Navier-Stokes equations and k-ω,sst turbulence model and the perfect gas equation are solved. Then the results of the numerical solution are compared and validated with experimental data. Numerical results showed good agreement with the experimental values. In the experimental test, Helium is injected into supersonic crossflow and so numerical simulation is started with Helium injection. In scramjet usually, hydrogen was used as fuel. Therefore, hydrogen fuel injection is used for the parametric study. In the case of air injection near the fuel injection, maximum fuel penetration with minimum stagnation pressure loss is achieved.

The correction of “Gouy va chowgan” (karnameh)made by the Ghasemi Gonabady published as enclosed to two volumes of seasonal journal of Ayeneye Mirath. This manuscript is aimed to make a critical correction on the matter with respect to the correctors, some points must need modification including: the year of versifying the “Gouy va chowgan mathnavi” is 947 instead of 977. The birthday of the Ghasemi Gonabadi mistakenly noted at 930, while versifying of Mathnavi of Shah Esmael Nameh" is 940, "the Gouy va chowgan" and “Leili va Majnun was versified in 947", "Shahrokh Nameh", "Khosrow va Shirin" and "ShahTahmasbnameh" in 950. Furthermore, the scientific method hasn’t been applied in the correction of the book especially in the preface and also the correctional method throught the book is not uniform and even sometimes the citations from other manuscripts are in the square bracket, but other times aren't. Even the important part from different manuscript is not shown as footnote or inside the manuscript. The present research has corrected the errors and faults of the correctors based on a logical and scientific method.

Planar inlet concepts play an important role in the design of supersonic propulsion systems. The inlet reduces the speed of supersonic flow by the oblique shock wave or an array of oblique shock waves and a final normal shock provides the subsonic flow after the throat of the diffuser. In this paper, a design method of Mach 3.0 supersonic multi-ramp inlet is explained; the geometry is designed and simulated by the numerical solver. Designing the inlets for the high supersonic Mach range between 3 and 5 is very challenging because of the viscosity interactions and the related effects on the propulsive efficiency. The considered inlet in this study is a mixed system which provides the required compression by a combination of the three external ramps and a subsonic diffuser. A computational code calculated the optimum dimensions numerically and a second order CFD solver has simulated the inlet operations with an accuracy of 10E-05. In addition to aerodynamic performance, advantages and challenges of such a combination, development of boundary layer and its interactions with the normal shock and performance of bleeding mechanism are simulated and studied. Finally, this paper presents compact details of design, simulation and viscosity effect of mixed compression surface.

This article reports the active control of base flows using the experimental procedure. Active control of base pressure helps in reducing the base drag in aerodynamic devices having suddenly expanded flows. Active control in the form of microjets having 0. 5 mm radius placed at forty-five degrees apart is employed to control the base pressure. The Mach numbers of the present analysis are 1. 7, 2. 3, and 2. 7. The length to diameter (L/D) ratio is varied from 10 to 1 and the nozzle pressure ratio (NPR) being changed from 1 to 10 in steps of 1 for base pressure measurements. The area ratio for the entire analysis is fixed at 2. 56. Wall pressure distribution along the enlarged duct is also recorded. No change in base pressure increase/decrease is thoroughly analysed as well. From the experimental investigation, it is found that control plays an important in modifying the base pressure without disturbing the wall pressure distribution. The base pressure variation is entirely different at L/D = 1 compared to a higher L/D ratio due to change in reattachment length and the requirement of the duct length at higher inertia levels. The quality of the flow in the duct in the presence and absence of control remained the same.

Supersonic inlet has a key role in the performance of air-breathing engine special in ramjet engines. The function of a ramjet engines diffuser is to decelerate the air velocity from its freestream at the intake to a combustor velocity which is compatible with the available flame velocity. Accurate design of inlet has an important effect on the performance of a ramjet system and its main parameters. In this study, an axisymmetric external compression supersonic inlet designed at Mach 3. Flow behavior for this type of inlet is more complicated than the two-dimensional inlet. Because of this character, a computer program for solving the equations of supersonic flow through the cone, and the relationship between the parameters and the principles of the axisymmetric inlet has developed which integrates the final geometry, including center body geometrical details, inlet cowling and subsonic channel as output. Since viscous forces cannot be ignored because they cause complex shock patterns and flow separation, the simulation and flow behavior pattern is modeled and validated by computational fluid dynamics software. For this purpose, the RNG K-ɛ model was used for flow turbulence modeling and second-order accuracy was used for discretization of convection term. The results show that the designed geometry can meet the desired performance requirements.

An improved delayed detached eddy simulation (IDDES) is carried out to investigate both the mean and the instantaneous flow characteristics of conical cavities fixed on a cone surface in a Mach 0. 9 freestream. Two model categories, a single cavity model with different length (L) to depth (D) ratio and a multi-cavity model that inserted the separation disk into a single cavity are studied. Results indicate that in case of a single cavity model, the cavity L/D ratio is the key parameter that influences mean flow structure and oscillatory characteristics. The bulk reverse flow structure can be broken up into smaller structures as L/D value reduces from 4. 0 to 0. 51 inside the cavity. Smaller longitudinal pressure gradients on the cavity wall and the thicker downstream boundary layer are observed when larger L/D values are present. The cavities with smaller L/D values can stimulate the pressure oscillation fundamental frequency as well as the acoustic tones to increase the value. Multi-cavity configurations through insertion of a separation disk into the single cavity are helpful in cutting the large reverse flow structure inside a cavity into a smaller, similar, coherent structure, and to reduce the overall cone drag. The insertion of the separation disk can modulate pressure oscillation peaks and sound pressure levels to higher frequency, however, they are not able to reduce the overall sound pressure inside the cavity. Pressure oscillations within each cavity of the multi-cavity configuration have a weak correlation.

Background and Aim: Although operation is the most appropriate treatment for Cauda Equina Syndrome, the effectiveness of operation on clinical symptoms is still under discussion. This study aimed to determine the prognosis of Cauda Equina Syndrome in patients with lumbar disk surgery in Al-Zahra Hospital of Isfahan City, Iran, from 2013 to 2015.Methods and Materials/Patients: In This prospective study, patients diagnosed with Cauda Equina Syndrome who underwent operation in Al-Zahra Hospital of Isfahan from 2013 to 2015 were followed up for two years and the effect of the surgery on the improvement of their clinical symptoms was investigated.Results: In this study, 33 patients with Cauda Equina Syndrome were evaluated. About 24-month follow-up of patients showed muscle weakness improvement in 26 (78.8%) of them. Of all 19 patients with urinary dysfunction, 18 (94.7%) recovered. Six (33.3%) cases improved the day after surgery, 6 (33.3%) cases in one month, 4 (22.2%) cases in six months, and 2 (11.1%) cases within 24 months after the surgery. All 4 (100%) patients with bowl disorder also recovered during the study. One (25%) of them improved the day after operation, 1 (25%) one month after the operation and 2 (50%) within 24 months following the operation.Conclusion: According to the results of this study, operation of the lumbar disks leads to improvement of Cauda Equina Syndrome, including recovery of sphincter disorders and muscle weakness, but considering the limitations of our investigation (including a small sample size), further studies are recommended in this area.

The generation of shock waves and their repercussions in high-speed vehicles are inevitable. Particularly, the hot plume from the aircraft exhaust ejecting at a high speed, as well as the emitted aeroacoustic noise, have several consequences. Besides, the occurrence of the supersonic core length and the emission of high screech noise are mostly due to the shock cells, prevailing in high-speed jets. Therefore, understanding the shock cell structures developed at the exit of aircraft or rocket nozzles is vital in improving mixing and thereby the noise characteristics. Essentially, non-circular nozzle shapes are well known for enhancing entrainment characteristics and mitigating the noise due to their differential spreading over the nozzle's perimeter. The current study examines the shock structures of circular, elliptic, and square jets at various sonic underexpansion levels. In this investigation, the nozzle geometries are considered to have the same exit area. The Nozzle Pressure Ratio (NPR) was adjusted to 3, 4, and 5 to achieve moderate and highly underexpansion conditions. The shadowgraph visualization method is used to study the development of shock cells from axisymmetric and asymmetric nozzles. It is interesting to observe that the incident and reflected shock structures exist only at moderate and high underexpansion levels. Besides, the elliptic and the square jets have distinctive flow patterns along their different axis planes. The intercepting shock appears on the elliptic jet in the minor axis rather than the major axis direction. The curvature of the intercepting shock wave was found to be greater for the elliptic jet than that for the circular jet. In addition, the square jet in the symmetry plane diverges from the jet centerline, but the jet in the diagonal direction converges. Moreover, the estimated shock cell lengths using shadowgraph images were compared to a theoretical model where the experimentally obtained results are in good agreement with the theoretical values.