Sajjad Sattari Articles List

List of Articles Sajjad Sattari

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1 - Numerical Simulation of the Supersonic Flow over Forward-Facing Step in Micro Couette Flow Using Direct Simulation Monte Carlo Method
Sajjad Sattari Mahsa Jahani Mofid Gorji-Bandpy

This work deals with a numerical study on forward-facing steps situated in a supersonic flow. The primary aim of this paper is to examine the sensitivity of the velocity, density, pressure and temperature due to step-height variations of such forward-facing steps. Effec More

This work deals with a numerical study on forward-facing steps situated in a supersonic flow. The primary aim of this paper is to examine the sensitivity of the velocity, density, pressure and temperature due to step-height variations of such forward-facing steps. Effects on the flowfield structure due to variations on the step height have been investigated by employing the Direct Simulation Monte Carlo (DSMC) method. The studied parameter contours for various values of step heights and profiles in three different sections of the channel are obtained. The results indicate that the fluid flow and temperature characteristics considerably depend on the step heights. The results was also compared with previous published works which showed excellent agreement. Manuscript profile
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2 - Comparison of Vibration Amplitude in Isfahan Subway Due to Track Structure- An Experimental Study
sajjad sattari Mohammad Saadat Sayed Hasan Mirtalaie mahdi salehi ali soleimani
10.30486/admt.2023.1973746.1392

Increasing the stability of structures and reducing the maintenance cost of slab track superstructures compared to ballasted tracks are among the reasons for the tendency to use this category of superstructures in the railway industry. Vibration reduction methods can be More

Increasing the stability of structures and reducing the maintenance cost of slab track superstructures compared to ballasted tracks are among the reasons for the tendency to use this category of superstructures in the railway industry. Vibration reduction methods can be divided into three categories, source, propagation path, and receiver. In general, the slab track structures in Iran are divided into three categories: direct fixation track (DFT), floating slab track (FST), and high resilient fastener (HRF). Although railway tracks are a safe, economical and fast transportation system and can lead to the strengthening of the tourism industry, in the long term, vibrations can damage many historical structures in the city of Isfahan. FST and HRF systems are used in the structure of Isfahan subway track. In this paper, the accelerations (longitudinal, lateral, and vertical) of the Isfahan subway vehicle were measured in 30 stations (15 go stations and 15 return stations). The results showed that the HRF system compared to the FST has a significant effect in reducing the range of vibrations and ultimately the safety of the train and the ride comfort. For example, in the area between Si-O-Se-Pol and Imam Hossein Square, due to the track structure type (HRF), the maximum acceleration and RMS acceleration are in the range of 1.5 and 0.3 m/s2, respectively, while in other stations these values were extracted up to 4 and 0.7 m/s2, respectively. Manuscript profile
Open Access Article
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3 - Evaluation of Sperling’s Index in Passenger and Freight Trains Under Different Speeds and Track Irregularities
sajjad sattari Mohammad Saadat Sayed Hasan Mirtalaie mahdi salehi ali soleimani
10.30486/admt.2023.1963242.1367

The two factors of track irregularity and train speed affect the dynamic behavior of rail vehicles and can lead to an increase in dynamic forces, a decrease in ride comfort, and derailment in some cases. In this paper, the effect of train speed increase and different co More

The two factors of track irregularity and train speed affect the dynamic behavior of rail vehicles and can lead to an increase in dynamic forces, a decrease in ride comfort, and derailment in some cases. In this paper, the effect of train speed increase and different conditions of track irregularity on ride comfort and ride quality are investigated. For this purpose, first, two freight and passenger train models have been modeled in UM software, and then the effect of train speed increase and track irregularities (different US federal classes) have been studied with Sperling’s index. A freight train with the model of 18-100 and 3-piece bogie and a TGV high-speed train with 10 wagons were simulated. The results showed that in Sperling’s index, with the increase in the train speed and irregularity amplitude, the value of ride comfort and ride quality generally increased. For example, in the passenger train and irregularity classes 5 and 4, with the increase in train speed from 10 to 100 m/s, the Sperling’s index values changed from 0.66 to 1.99 and from 0.78 to 2.25, and increased 200% and 188%, respectively. In other words, at a speed of 10 m/s, passengers' comfort is just noticeable, while at a speed of 100 m/s and class 4, the situation is more pronounced but not unpleasant and the system should be monitored. Manuscript profile
Open Access Article
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4 - Simulation of a Freight Train and The Effect of Wheel Flat Defect on The Wheel/Rail Dynamic Forces
Sajjad Sattari Mohammad Saadat Sayed Hasan Mirtalaie Mehdi Salehi Ali Soleimani

Wheel/rail interaction is one of the most important research topics in railway engineering and generally includes impact response, vibrations, and track safety. Track structure failures caused by wheel/rail impact dynamic forces can lead to significant economic loss thr More

Wheel/rail interaction is one of the most important research topics in railway engineering and generally includes impact response, vibrations, and track safety. Track structure failures caused by wheel/rail impact dynamic forces can lead to significant economic loss through damage to rails, ballast, fastening system, etc. Wheel/rail impact forces occur due to defects in wheels and/or rails such as wheel flats, irregular wheel profiles, rail corrugation, etc. A wheel flat can cause a large dynamic impact force as well as high frequency forced vibrations, which will eventually lead to damage to the train and track structure. In the present work, a freight train (3D model) was used to analyze the dynamic impact caused by the wheel flat using UM software. The effects of wheel flat depth and length (0, 0.2, 0.5, 1, 1.5, 2, and 3 mm) at two speeds of 50 and 80 km/h on wheel/rail dynamic forces have been investigated. The results showed that the presence of a wheel flat defect significantly increases the wheel/rail dynamic impact. For example, by increasing the wheel flat depth to 3 mm, the values of maximum force at speeds of 50 and 80 km/h have changed by about 235% and 400%, respectively. Manuscript profile

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List of Articles Sajjad Sattari