Issue 4
JTAM, Sofia, vol. 55 Issue 4 (2025)

DROP TEST VALIDATION OF A VIRTUAL PROTOTYPE OF EV BATTERY PACK

Georgi Todorov, Konstantin Kamberov, Todor Gavrilov, Konstantin Dimitrov
Technical University - Sofia, FIT, Laboratory ``CAD/CAM/CAE in Industry'', 8, ``Kl. Ohridski'' Blvd., 1797 Sofia, Bulgaria


This study explores the validation process of a drop test virtual FEM experiment of a complex structure - battery pack. A physical prototype has been manufactured and subjected to drop tests, where its impact behavior has been examined through the use of high-speed imaging and visual tracking software. Different indicators have been used in order to validate the virtual analysis through adjusting materials, boundary conditions and analysis settings. A validated virtual analysis gives an insight of the deformations and stresses in different areas of the tested assembly that can be used for further geometry optimization and/or certification.

JTAM, Sofia, vol. 55 Issue 4 pp. 387-401 (2025), [Full Article]

AN APPROXIMATE SOLUTION FOR THE FLOW OVER A FINITE SINUSOIDAL OBSTACLE WITH A HIGH WEBER NUMBER EFFECT AND ZERO GRAVITY

May Manal Bounif1, Abdelkader Gasmi2
1Higher School of Management and Digital Economy, Kolea, Algeria
2Laboratory of Pure and Applied Mathematics, Faculty of Mathematics and Informatics, University of M'sila, Algeria

This paper considers the problem of inviscid and incompressible flow with a free surface over sinusoidal obstacles of finite length placed in the bottom with finite length. The flow is considered by neglecting the gravity effect, but we take into account the surface tension effect. Applying the first order perturbation technique in conjunction with the Hilbert transformation, we provide an approximate solution to the boundary value problem with mixed boundary conditions arising from the flow problem. The unknown free-surface profiles are established for each large value of the Weber number. The obtained results reveal the simplicity of the used method; they also provide approximate solutions to these kinds of problems.

JTAM, Sofia, vol. 55 Issue 4 pp. 402-415 (2025), [Full Article]

MAGNETO SOUND IN PLASMA AND NONLINEAR OPTICS ON MODIFIED TRUNCATED EXPANSION METHODS FOR THE ANALYTICAL SOLITON OF FIFTH ORDER (1+1) DIMENSIONAL TRIPLE NON-LINEAR PARTIAL DIFFERENTIAL EQUATIONS IN MATHEMATICAL PHYSICS AND MECHANICS

Satyajit Mohapatra, Saumya Ranjan Jena
Department of Mathematics, School of Applied Sciences, Kalinga Institute of Industrial Technology (KIIT) Deemed to be University, Bhubaneswar-751024 Odisha, India

In this manuscript, two modified truncated expansion methods (i.e MTEM-I and MTEM-II) are built up to obtain analytical solution (i.e so called traveling wave solutions) for triple (1+1) dimensional nonlinear~partial differential equations (NLPDEs)such as Sawada-Kotera equation (SKE), generalized Korteweg-de Vries equation (GKdVE) and Kaup-Kuperschmidt equation (KKE), which have been widely used in mathematical physics. The present topic minimizes the complex nature and non-integrable characteristics to obtain solution of NLPDEs. To demonstrate the influence of the parameters, 3D plots are surfed for triple NLPDEs. certification.

JTAM, Sofia, vol. 55 Issue 4 pp. 416-431 (2025), [Full Article]

EXPERIMENTAL ANALYSIS OF HYDRAULIC JUMP LENGTH IN ROUGH-BEDDED COMPOUND CHANNELS

Khechiba Haroun1, Ali Ghomri2, Djamel Besser1, Ibtissam Herri1
1UDERZA Unit, Faculty of Technology, University of El Oued, 39000 El Oued, Algeria
2Research Laboratory in Underground and Surface Hydraulics, University of Biskra, Department of Hydraulics and Civil Engineering, University of El Oued, Algeria

This study explores how bed roughness affects the length of hydraulic jumps in a rectangular compound channel under zero slope. Experiments were done in a 10 m flume with a compound cross-section (minor bed: 14.4 cm, major bed: 25 cm), using plastic roughness elements (ϵ = 6-12 mm). Different flow rates and upstream depths were tested. Results show that increased roughness shortens jump length (Lj) by enhancing turbulence and momentum transfer. The minor bed's relative roughness (ϵ/b) had the strongest effect. Dimensionless equations were developed linking Lj/h1 with the Froude number (F1) and roughness. Findings underline the role of bed roughness in managing jumps, with implications for energy dissipation and flood control systems.

JTAM, Sofia, vol. 55 Issue 4 pp. 432-443 (2025), [Full Article]

CFD INVESTIGATION AND VALIDATION OF HEAT TRANSFER IN A SOLAR AIR COLLECTOR UNDER NATURAL AND FORCED CIRCULATION

Liyes Aguedal1, Djaffar Semmar2
1Department of Mechanical Engineering, University of Mentouri Brothers-Constantine 1, Constantine, 25000, Algeria
2Surface de Treatment and Materials Laboratory, Department of Mechanical Engineering, Faculty of Technology, University of Blida 1, Soumâ Street No. 270, 09000, Blida, Algeria

This study performs a computational fluid dynamics (CFD) analysis of a solar air collector (SAC) under natural and forced circulation, validated against experimental data. A 2D ANSYS Fluent model with a structured mesh simulated thermo-hydraulic behavior, including Boussinesq buoyancy and transient solar loading. In natural circulation, outlet temperatures peaked at 355 K around 13:00-14:00, with < 3% deviation from experiments. Vertical gradients of ΔT ≈ 30 K indicated buoyancy-driven flow. Under forced circulation, the outlet temperature peaked earlier at 333.51 K, showing better thermal uniformity due to a thinner boundary layer. Forced convection improved thermal efficiency by 39% over natural circulation but required additional pumping. CFD proves valuable for optimizing SAC designs, balancing efficiency, simplicity, and operational costs.

JTAM, Sofia, vol. 55 Issue 4 pp. 444-459 (2025), [Full Article]

LONGITUDINAL RIBS EFFECT ON THE ENHANCEMENT OF HEAT TRANSFER IN TAYLOR-COUETTE-POISEUILLE FLOW

Ahmed Daimallah1, Mohamed Lebbi2, Lyes Boutina2
1LEMI, Faculty of Technology, University M'hamed Bougara of Boumerdes, Avenue de l'indépendance 35000 Boumerdes, Algeria
2Unité de Recherche Appliquée en Energies Renouvelables URAER, Centre de Développement des Energies Renouvelables, CDER, 47133 Ghardaïa, Algeria

In this study, a three-dimensional simulation was conducted to examine the effect of rib integration on the heat transfer characteristics in Taylor-Couette-Poiseuille flow (TCPF). The ribs are fixed to the periphery of the inner cylinder of the system studied. Three cases were analyzed: 4, 8, and 16 ribs. Initially, the study considers purely axial flow with a stationary inner cylinder, while the next phase evaluates the combined influence of axial flow and cylinder rotation. The findings reveal that the configuration with four ribs achieves the most significant heat transfer improvement, with an increase of up to 312% at higher Reeff values and approximately 103.6% at lower Reeff values.

JTAM, Sofia, vol. 55 Issue 4 pp. 460-474 (2025), [Full Article]

LIVER ELASTICITY AS A MEASURE OF LIVER DAMAGE

S. Donev1, V. Pencheva1, D. Petrova1, R. Tsrancheva1, M. Kirilova2,3
1Department of Propaedeutics of Internal Diseases, UMHAT
2Faculty of Pharmacy, Medical University - Sofia, Bulgaria
3Institute of Mechanics, Bulgarian Academy of Sciences, Bulgaria

A monitoring of liver elasticity is important in managing viral hepatitis because liver damage leads to hepatocellular carcinoma. The prospective study was conducted over a 24 month period among newly diagnosed patients with viral hepatitis B (HBV) and C (HCV). The aim of the study was to predict the cases of hepatocellular carcinoma (HCC) according to liver elasticity and age of the patients. The patients in risk are those whose liver stiffness (LS) is over 13 kPa and was established that they are between 18-25%. The results showed that hepatitis C and age over 50 yrs. leads to high level of liver stiffness. The patients over 50 yrs have 3.25 times higher odds of increased LS compared to those under 50 in case of HCV and 2.15 times higher odds in case of HBV.

JTAM, Sofia, vol. 55 Issue 4 pp. 475-485 (2025), [Full Article]

MAGNETOHYDRODYNAMICS FLOW IN DOUBLE-LID L-SHAPED CAVITY WITH LOCAL REFINEMENT

Ebutalib Çelik1, Merve Gurbuz-Caldag2
1Department of Computer Technologies, Çanakkale Onsekiz Mart University, Çanakkale, Turkey
2Department of Mathematics, TED University, Ankara, Turkey

This study presents new insights into structures of magnetohydrodynamics flow in a double lid-driven L-shaped cavity under an oriented magnetic field. The governing equations are presented using the stream function-vorticity approach and solved numerically. Radial basis function-finite difference method utilizing polyharmonic splines is proposed to achieve local refinement. Flow topologies are examined for problem parameters, including the inclination angle, Hartmann number, and Reynolds number. The results indicate that as the strength of the magnetic field increases, the Lorentz force becomes the dominant factor, making the impact of the Reynolds number on flow negligible. The strength and inclination angle of the magnetic field play crucial roles in influencing the flow structure by altering the number, position, and type of critical points.

JTAM, Sofia, vol. 55 Issue 4 pp. 486-502 (2025), [Full Article]

ARTERIAL SOLID MECHANICS. A BRIEF REVIEW AND BULGARIAN "IMPRINT"

Alexander Rachev
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria

This paper provides an overview of research in arterial solid mechanics for readers who may not have expertise in the field of biomechanics. The review explores whether a healthy artery functions as an "intelligent" organ. A brief description of the biological and mechanical processes that govern arterial performance is followed by an overview of typical experimental findings and mathematical models describing the passive, active, and remodeling behavior of healthy arteries. The review includes critical commentary based on the author's perspective. The term "Bulgarian imprint" highlights the significant contributions of Bulgarian scientists, frequently in collaboration with international partners, to arterial biomechanics. When cited, the corresponding papers are denoted in the reference list by an asterisk.

JTAM, Sofia, vol. 55 Issue 4 pp. 503-520 (2025), [Full Article]