Computer Code Research Articles

Design of Rocket Engine Nozzle Using Method of Characteristics

Abstract: This report focuses on the design of a 2D theoretical layout of a rocket engine nozzle. Convergent and divergent are to be designed separately with the focus on divergent part for a minimum length nozzle. The divergent part is to be designed using method of characteristics with left and right running characteristics using the known (sonic) values at the throat of the convergent-divergent nozzle. These characteristics would be pressure, density, velocity and temperature. A computer code has been designed to calculate the values of these characteristics and the end characteristics at the exit. CFD analysis has also been carried out on the designed nozzle using commercial software ANSYS.

SIMMER code two-fluid model well-posedness and stability for simulating liquid metal (lead–lithium eutectic), water vapor, and non-condensable gases multi-component multi-phase flows

Liquid metals are employed as a coolant in liquid metal fast reactors (LMFR) and are considered breeders and coolants for future power-producing fusion reactors. The interaction of liquid metals with other coolants, such as air and water, is one of the possible occurrences in liquid metal-cooled reactors. Although the SIMMER-III computer code is currently in the validation and verification phase, it is a prospective candidate code for correctly investigating possible accidents. This study aims to determine the stability and well-posedness of the SIMMER-III code Eulerian-Eulerian two-fluid model (TFM) under any such accident scenario. This work also considers the influence of the virtual mass force and diffusion forces in momentum on TFM stability in accelerated liquid metal, steam, and non-condensable gaseous flows throughout all flow regimes. The characteristics method is used to assess the ill-posed nature of TFM for all types of accidents and accident scenarios in a hypothetical simplified system model with several components (Lead–Lithium, non-condensable gases, and water vapor). It has been discovered that the analysis findings vary from the air and water two-component two-phase flows (characteristics roots spectrum and error growth rate patterns) and are particularly sensitive to the diffusion and virtual mass coefficients. This is because liquid metals have a higher density than liquid water and steam, resulting in strong virtual mass forces and weak diffusion forces in liquid-metal and gas two-phase flows. Because of the extensive range of possible interactions between fluxes of different components, producing an accurate representation of diffusion in multi-component mixtures is difficult. Because of this, it is strongly suggested that the virtual mass coefficient and diffusion coefficients be handled more accurately for these kinds of flows. The values of these coefficients significantly affect how accurate proposed TFM predictions are, but there hasn't been much research on how to estimate them. The study also sheds light on the model's accuracy and highlights the areas where the model's predictions will be mathematically trustworthy.

Mixed quantum/classical theory (MQCT) approach to the dynamics of molecule-molecule collisions in complex systems.

We developed a general theoretical approach and a user-ready computer code that permit study of the dynamics of collisional energy transfer and ro-vibrational energy exchange in complex molecule-molecule collisions. The method is a mixture of classical and quantum mechanics. The internal ro-vibrational motion of collision partners is treated quantum mechanically using a time-dependent Schrödinger equation that captures many quantum phenomena including state quantization and zero-point energy, propensity and selection rules for state-to-state transitions, quantum symmetry and interference phenomena. A significant numerical speed up is obtained by describing the translational motion of collision partners classically, using the Ehrenfest mean-field trajectory approach. Within this framework a family of approximate methods for collision dynamics is developed. Several benchmark studies for diatomic and triatomic molecules, such as H2O and ND3 collided with He, H2 and D2, show that the results of MQCT are in good agreement with full-quantum calculations in a broad range of energies, especially at high collision energies where they become nearly identical to the full quantum results. Numerical efficiency of the method and massive parallelism of the MQCT code permit us to embrace some of the most complicated collisional systems ever studied, such as C6H6 + He, CH3COOH + He and H2O + H2O. Application of MQCT to the collisions of chiral molecules such as CH3CHCH2O + He, and to molecule-surface collisions is also possible and will be pursued in the future.

Simple Method for Predicting the Heats of Formation of Energetic Metal–Organic Frameworks

Abstract The heats of formation (HOF) of energetic materials is crucial in determining their performance. A novel approach has been introduced to accurately predict the condensed phase HOF of energetic metal-organic frameworks (EMOFs). The experimental condensed phase HOF data of 63 EMOFs were utilized to develop and evaluate the model. This model relies on particular chemical bonds, elemental composition, and some of the specific structural parameters that can be obtained from the chemical structures of EMOFs. This model can be easily applied to EMOFs with intricate compositions and structures, without the need for complicated computer codes. Statistical parameters along with the internal and external validation approaches were employed to assess the accuracy, precision, goodness-of-fit, and goodness-of-prediction of the model. Values of the coefficients of determination in training set, as well as internal and external validation, i.e., R2, $${\text{Q}}_{{{\text{LOO}}}}^{2}$$, $${\text{Q}}_{{5{\text{-fold}}}}^{2}$$, and $$R_{{{\text{External}}}}^{2}$$ are 0.96, 0.93, 0.91, and 0.94, respectively.

Mining in Russia. Cryptocurrencies as investment

In modern conditions, when parity international financial and monetary relations are turning from traditional instruments of economic interaction into instruments of neocolonial political pressure and blackmail of economically strong countries against weaker ones, the need for a new global financial order and monetary standard, that would be independent of the will of any central bank, but with a value as reliable as that of modern fiat currencies, is increasingly realized. Today, the global economy feels the urgent need for fundamentally new opportunities for market interaction and monetary exchange. Cryptocurrencies have become such tools — electronic decentralized money issued by specific individuals in specialized open computer networks through the transformation of electricity into fixed computer codes. The process of such transformation is called mining, which uses ASIC miners as computer equipment to obtain cryptocurrency. The concept of cryptocurrencies and the specifics of investing in them are considered. The characteristic is presented of the current state and dynamics of the development of the crypto market. The possibilities and methods of forecasting the development of the cryptocurrency market are shown both using classical methods of economic forecasting and a fundamentally new methodology based on the current assessment of the psychological state of participants in the crypto market and their readiness to commit certain economic actions. An assessment is given of the possibilities of investing in mining as a technology for mining cryptocurrencies. Requirements to special mining equipment — ASIC miners — are described. An assessment is given of the prospects for the development of the crypto economy.

Laser Doppler Fluximetry in Cutaneous Vasculature: Methods for Data Analyses

Introduction: Acquisition of a deeper understanding of microvascular function across physiological and pathological conditions can be complicated by poor accessibility of the vascular networks and the necessary sophistication or intrusiveness of the equipment needed to acquire meaningful data. Laser Doppler fluximetry (LDF) provides a mechanism wherein investigators can readily acquire large amounts of data with minor inconvenience for the subject. However, beyond fairly basic analyses of erythrocyte perfusion (fluximetry) data within the cutaneous microcirculation (i.e., perfusion at rest and following imposed challenges), a deeper understanding of microvascular perfusion requires a more sophisticated approach that can be challenging for many investigators. Methods: This manuscript provides investigators with clear guidance for data acquisition from human subjects for full analysis of fluximetry data, including levels of perfusion, single- and multiscale Lempel-Ziv complexity (LZC) and sample entropy (SampEn), and wavelet-based analyses for the major physiological components of the signal. Representative data and responses are presented from a recruited cohort of healthy volunteers, and computer codes for full data analysis (MATLAB) are provided to facilitate efforts by interested investigators. Conclusion: It is anticipated that these materials can reduce the challenge to investigators integrating these approaches into their research programs and facilitate translational research in cardiovascular science.

Recent observations of the rotation of distant galaxies and the implication for dark matter

Recent measurements of gas velocity in the outer parts of high redshift galaxies suggest that steeply falling rotation curves may be common or even universal in these galaxies, in contrast to the near universal flat, non-declining rotation curves in nearby galaxies. The aim was to investigate the implications of these postulated steeply falling rotation curves for the role of dark matter in galaxy formation. Using an established computer code, the collapse of dark matter and baryonic matter together, starting with a variety of initial conditions, was simulated for comparison with the observed rotation curves. A simulation of collapsing baryonic matter on its own without dark matter was also carried out. The masses of the protogalaxies were chosen to produce a stellar disc in the same mass range as the observed galaxies at roughly the same redshift. As soon as a smooth stellar disc was formed in the baryonic matter, with properties similar to the observed high redshift galaxies, the computed rotation curves were without exception relatively flat to large radius in the gas disc. Only a simulation without a dark matter halo was able to reproduce the observed rotation curves. This implies that if the high redshift steeply falling rotation curves turn out to be common, then the standard scenario of galaxy formation by baryonic matter falling into the potential well of a massive dark matter halo must be wrong, unless there is pressure support via velocity dispersion significantly higher than has so far been observed or resulted from our simulations. It would also imply that for these galaxies the flat rotation curves at low redshift must be due to dark matter which has subsequently fallen into the galactic potential well, or there must be some other explanation for their contemporary flat rotation curves other than dark matter.

Trinitroethyl hydrazides of dicarbonic acids – Energetic compounds with high oxygen and nitrogen content

AbstractMany currently used energetic materials need to be replaced with new compounds due to toxicity or other drawbacks. Among these is the oxidizer ammonium perchlorate, often used in solid state propellants, which itself, as well as its combustion products, poses health and environmental issues. Herein, three new polynitro energetic compounds are presented containing trinitroethyl moieties. Starting from easily available starting materials, such as malonic acid ethylester, diglycolic and diaminodiacetic acid, simple and straightforward syntheses were performed to obtain first the corresponding hydrazides and subsequently the trinitroethyl hydrazides in good yields and high purity. These compounds have a positive oxygen balance (assuming to the formation of CO), a high oxygen and nitrogen content and moderate densities. Full characterization was performed by NMR spectroscopy, vibrational analysis and elemental analysis. By using the Gaussian program package, the heats of formation were calculated and the energetic parameters were estimated utilizing the EXPLO5 computer code.

Energy flow investigations of Rayleigh-Plesset equation for cavitation simulations

Nonlinear Rayleigh-Plesset Equation (RPE) for cavitation simulations is investigated using energy-flow theory. Nondimensional RPE affected by Reynolds-number, surface-tension, bubble-pressure, and liquid static-dynamic pressure ratio is derived to examine its equilibrium points with stability, possible periodical/chaotic motions by the energy-flow criteria. An example is numerically analyzed to illustrate the developed method. Five cases of the example reveal: 1) It is a damped system, where initial disturbances are gradually reduced with its phase point tends to its stable equilibrium-point; 2) Reynolds-number affects the damping of system, large one corresponds small damping; 3) Bubble-pressure, surface-tension and liquid static-dynamic pressure ratio affect the position of equilibrium point; 4) Periodical orbit appears only in forced vibrations, in which free vibration is reduced with time forward and the system finally shows a stable periodical oscillation; 5) Energy flow criteria for chaotic motions is not reached, and there are no chaotic motions for the cases of example. Numerical simulations confirm the developed energy-flow means with available computer code is effective to investigate generalized RPEs to reveal their inherent characteristics affected by required parameters in engineering cavitation analysis and designs, such as considering mass transports across the boundary of bubble by evaporation or condensation of liquids.

Design, assembly and testing of an upgraded aeroacoustics wind tunnel facility

The Aeroacoustics Laboratory in the Department of Aerospace Engineering at Penn State currently serves several areas of experimental research. Most notable in the laboratory is the Anechoic Chamber of which the Aeroacoustics Wind Tunnel is an integral part. In recent years the dominant areas of research have included model aircraft exhaust jets and model rotors for helicopter applications involving detailed noise experiments. In the jet noise area, the applications have included aircraft in both flyover and take-off configurations. In the flyover application the air flow surrounding the exhaust jet has a significant effect on the radiated noise and must be simulated to produce experimental results that will be most useful in preliminary design of noise suppression applications. The Aeroacoustics Wind Tunnel at Penn State serves the purpose for this simulation. During aircraft take-off, the aircraft airspeed is in a range exceeding 250 ft per second, or Mach number of over M = 0.22. In the years preceding 2022, the velocity of the free jet flow of the Penn State facility was limited to less than 200 ft/sec. This paper reports on a project to design upgrades to the existing wind tunnel to improve the test section flow velocity to values closer to the 250 ft/sec target. The approach began with a preliminary design of the return flow ducting to convert the open jet, open return wind tunnel to a closed return tunnel. The concept is to make use of the flow energy in the exhaust of the tunnel to boost the input energy to the inlet fan that drives the flow to the test section. An integral part of the preliminary design involved making use of an upgraded flow analysis computer code to predict the gain in test section velocity of the new facility. For the available horsepower of two fans in the facility, the configurations of the existing and upgraded wind tunnel were entered into this analysis code based on a quasi-one-dimensional formulation. The code included empirical data formulated to include the various shapes of the components of the tunnels. The relative flow velocities in each section used simple incompressible continuity to calculate all velocities in the component sections. The average dynamic pressure in each section is calculated from the flow (constant) density and the velocity squared. Each section had a non-dimensional pressure loss parameter calculated from empirical data (from the relevant literature). The basic code (using the Excel algorithms) was based on a predictor-corrector concept in which the calculation was initialized with the estimated velocity and pressure of the flow at the entrance to the test section. The loss in each following section is estimated to determine the loss in the total pressure and the cumulated loss compared to the gains made at the two fans in the circuit. The initial guess is adjusted based on the total pressure value at the end of the circuit. During the related experiments, measurements of the total and dynamic pressure were performed at several joints between sections and compared to the values predicted in the analysis code. Various settings of the horsepower of the drive fans were used and the results were compared to flow measurements for the tunnel configurations (predominantly for the open return and closed return tunnel setups available before and after the upgrade project.) Results of the analysis and experiments are presented and analyzed together with the remaining activities planned for the coming months.

Thermosolutal and hydromagnetic performance of radiative hybrid nanofluid in a wavy porous enclosure with a plus-shaped baffle

The objective of this article is to explore the thermosolutal transmission rates with hydromagnetic Fe3O4-H2O nanofluid and Fe3O4-Cu-H2O hybrid nanofluid flow in a partially heated wavy porous enclosure with a plus-shaped baffle. A portion of length b on the bottom border is heated and soluted uniformly, while the rest portions of the bottom wall are assumed as adiabatic. The side curved borders are considered as cold and low concentration, while the adiabatic condition is imposed in the upper flat border. A plus-shaped cold baffle is located at the geometric center of the chamber. The porous cabinet is filled with a radiative Fe3O4-H2O nanofluid and Fe3O4-Cu-H2O hybrid nanofluid. The streamfunction (ψ)- vorticity (ζ) form incorporating the energy and species transport equations of coupled Navier-Stokes governing equations are solved by an efficient compact scheme. We have validated our in-house computational code with reliable published numerical and experimental works. This work explores the impacts of various well-defined parameters such as Rayleigh number (104≤Ra≤106), Hartmann number (0≤Ha≤40), Darcy number (10−4≤Da≤10−2), buoyancy ratio (N=1), Lewis number (1≤Le≤20), radiation parameter (1≤Rd≤10), heater size (0.2≤b≤0.8), volumetric heat source/sink coefficient (−10≤Q≤10) and solid volume fraction (0.0≤ϕhnp≤0.04) of the hybrid nanofluid. We have found that for the change in the radiation parameter (Rd) from 1 to 10, energy transfer is improved by 150.67% for Fe3O4-Cu-H2O hybrid nanofluid and 149.80% for Fe3O4-H2O nanofluid whereas solutal transfer is diminished by 4.76% and 4.83%, respectively. Our result revealed that Fe3O4-Cu-H2O hybrid nanofluid is more useful than Fe3O4-H2O nanofluid in the case of double diffusion.

Development of a numerical model for disassembly phase of hypothetical core disruptive accident and application to a medium-sized mixed oxide fuelled fast reactor

Safety assessment of fast reactors involves analyzing Hypothetical Core Disruptive Accidents (HCDA) that could result in reactor core disassembly. HCDA is generally analyzed in three distinct phases that include pre-disassembly, disassembly and post-disassembly phases. In the present work, a new coupled neutronics-hydrodynamics computer code called FAst Reactor DISassembly (FARDIS-1) is developed in 2-D cylindrical coordinate geometry to model the super-prompt critical power excursion during the disassembly phase of HCDA in a sodium-cooled fast reactor (SFR). The modelling approach followed is essentially similar to the one used in VENUS-II code but with a few improvements. The code is benchmarked against the predictions of VENUS-II for a sample case of HCDA in the FFTF reactor model. This is followed by an analysis of the disassembly phase in a medium-sized (500 MWe) mixed oxide fuelled fast reactor. Two cases are assumed at the beginning of the disassembly phase: a sodium voided core (conservative) and a partially voided core (realistic) and the influence of several core neutronics parameters on the transients is elucidated through parametric studies. The peak power, thermal energy release, peak pressure, maximum temperature and work-potential are estimated and their trends are discussed.

Simulation of a two-phase loop thermosyphon using a new interface-resolved phase change model

The remarkable progress made in power electronics has been coupled with the miniaturization of systems, requiring high-performance cooling. A solution that has garnered significant interest involves the use of two-phase loops, in which heat transfer is associated with the phase change of the working-fluid. This paper aims at modeling two-phase flow with separated phases in a gravity-driven two-phase loop. The Volume-of-Fluid method is employed to capture the moving interface. Amid the variety of the phase change models available in the literature, we have chosen to employ a hybrid model: a subgrid-scale model to generate phase change at the wall in the absence of an interface, and a interface-resolved model for phase change at pre-existing liquid-vapor interfaces. These models have been implemented in the OpenFOAM computational code. The developed solver makes possible the simulation of compressible laminar two-phase flow with diabatic liquid-vapor phase change. Conjugate heat transfer between the wall and the fluid is also taken into account. Two-dimensional numerical simulations demonstrate that the developed solver is capable of reproducing flow regimes obtained from experiments, including the formation of Taylor bubbles and the propulsion of liquid from the evaporator to the condenser during geyser boiling. Furthermore, this study examines how the filling ratio affects flow regimes and performance.

Ab-initio study of potassium-based halide perovskites for photovoltaic and opto-electronic applications

A first principle Density Functional Theory (DFT) analysis was applied to investigate the structural, electronic, and optical properties of cubic perovskites KXB3 (X= Ge, Sn; B= Cl, Br). Using the computational code WIEN2K, the corresponding properties have been studied through the use of Generalized Gradient Approximation. Experimental values of lattice constants are consistent with those derived from calculations. The wide direct band gap of 1.5–2 eV (M-M) is confirmed by the electronic band structure. This behavior suggests that the compounds under study are semiconducting KXB3 (X= Ge, Sn; B= Cl, Br) halide perovskite materials are a promising alternative to photovoltaic semiconductors because of their appealing optical properties, as confirmed by a variety of optical properties. Because of their advancement in perovskites, these materials can captivate the world. So, these perovskites materials can captivate world due to its advancement in Opto-electronic application especially in photovoltaic area.

Numerical investigation of heat transfer improvement in a latent thermal energy storage system using a composite of phase change material and nanoparticles in a porous medium

In the present study, the flow field and heat transfer in an energy storage tank are simulated. The Phase Change Material (PCM) in the present study is paraffin, which is converted to a liquid phase by the introduction of a high-temperature fluid (80 °C) and then the cold fluid enters the flow-carrying tubes, causing the melt to freeze. In the freezing (discharge) phase, the heat released from it increases the temperature of the fluid. Tubes in tank configurations are also used in latent thermal energy storage, which also performs well in terms of heat transfer. In this research, the use of special geometry with special and practical boundary conditions in order to estimate the charging and discharging behavior of the process of melting and freezing nano-phase change materials in it, as well as the instantaneous examination of the temperature field, melting and freezing by using a computer code using the finite volume method, can distinguish the results of this research from other studies. The results of this research show that, the shape of the tube and storage tank is slightly different from the shell-tube type, in which the Heat Transfer Fluid (HTF) flows through the tubes and these tubes also pass through a PCM tank. The study of the effect of porosity coefficient of porous medium shows that the rate of phase changes in porous medium with porosity coefficient of 0.95 is more than porosity coefficient of 0.97. In addition, by adding nanoparticles to paraffin the melting process takes place in a short time. According to the results, the nanoparticles added to the PCM accelerate heat transfer while maintaining energy storage capacity.

Numerical modeling of PFAS movement through the vadose zone: Influence of plant water uptake and soil organic carbon distribution

In this study, we investigated the effects of soil organic carbon (SOC) distribution and water uptake by plant roots on PFAS movement in the vadose zone with a deep groundwater table under temperate, humid climate conditions. Two series of numerical simulations were performed with the HYDRUS computer code, representing the leaching of historical PFOS contamination and the infiltration of water contaminated with PFOA, respectively. We considered soil profiles with three distributions of SOC (no SOC, realistic SOC distribution decreasing with depth, and uniform SOC equal to the content measured in topsoil), three root distributions (bare soil, grassland, and forest), and three soil textures (sand, sandy loam, and loam). The SOC distribution had a profound impact on the velocity of PFOS movement. The apparent retardation factor for realistic SOC distribution was twice as large as for the scenario with no SOC and more than three times smaller than for the scenario with uniformly high SOC content. We also showed that the root distribution in soil profoundly impacts the simulations of PFAS migration through soil. Including the root zone significantly slows down the movement of PFAS, primarily due to increased evapotranspiration and reduced downward water flux. Another effect of water uptake by plant roots is an increase of PFAS concentrations in soil water (evapo-concentration). The evapo-concentration and the slowdown of PFAS movement due to root water uptake are more significant in fine-textured soils than in sand.

Computational Codes for Fast Neutrons and Gamma Ray Interactions Coefficients in Different Material

In this research, many materials used as shields against ionizing radiation (neutrons and gamma rays) were studied. Seven glass systems compounds and five polymeric compounds were used to test their effectiveness in attenuating fast neutrons. These compounds are (S1-S7) as shown in table (1) and polymeric compounds as shown in table (3), many attenuation coefficients for these compounds were calculated through the use of a computer program called (SAZ) written in the Python programming language, which is used to calculate a number of basic parameters based on certain semi-empirical equations. The results showed that the sample (S7) and C9H9O is the best glass system compound and polymeric compound for neutrons attenuation, because they have a largest value of ΣR. Also, a number of Eco-friendly metallic compounds as shown in table (2) were used, to test them in shielding against gamma rays. The mass attenuation coefficient was calculated through the NIST-XCOM program for a range of energies starting from 59.53 keV up to 1 GeV. These compounds differed in their ability to attenuate gamma rays, as the results showed that the best studied compound against gamma rays was the PbS compound because it contains the Lead element, which has a largest atomic number.

Decoding the Atmosphere: Optimising Probabilistic Forecasts with Information Gain

Probabilistic prediction models exist to reduce surprise about future events. This paper explores the evaluation of such forecasts when the event of interest is rare. We review how the family of Brier-type scores may be ill-suited to evaluate predictions of rare events, and we offer an alternative to information-theoretical scores such as Ignorance. The reduction in surprise provided by a set of forecasts is represented as information gain, a frequent loss function in machine learning training, meaning the reduction in ignorance over a baseline having received a new forecast. We evaluate predictions of a synthetic dataset of rare events and demonstrate the differences in interpretation of the same datasets depending on whether the Brier or Ignorance score is used. While the two types of scores are broadly similar, there are substantial differences in interpretation at extreme probabilities. Information gain is measured in units of bits, an irreducible unit of information, that allows forecasts of different variables to be comparatively evaluated fairly. Further insight from information-based scores is gained via a similar reliability–discrimination decomposition as found in Brier-type scores. We conclude by crystallising multiple concepts to better equip forecast-system developers and decision-makers with tools to navigate complex trade-offs and uncertainties that characterise meteorological forecasting. To this end, we also provide computer code to reproduce data and figures herein.

Scaling methodologies and similarity analysis for thermal hydraulics test facility development for water-cooled small modular reactor

Small modular reactors (SMRs) represent a promising option for providing clean and sustainable energy due to their potential for enhanced safety, reduced capital costs, and increased siting flexibility. However, new reactor systems require the development and operation of representative scaled-down test facilities to support the verification and validation of system computer codes and models. This study reviews the research on scaling methodologies and similarity principles pivotal in developing non-nuclear integral effects test and separate effects test facilities for water-cooled SMRs. The study focuses on a review of the scaling methods, similarity approaches, and possible challenges posed by the unique and compact design features of integral-pressurized water reactor-type SMRs, and their representative test facilities. This study also reviews previous research related to scaling and similarity methodologies and provides insights into design considerations for achieving prototypic conditions in test facilities. The findings and recommendations emphasize the broader impact of appropriate scaling and similarity principles to ensure meaningful and transferable results from non-nuclear test facilities to accelerate the safe and efficient deployment of next-generation water-cooled SMRs.

Energy Convergence in a Structure Optimization and Vibrational Modes of Some Acene Molecules

Acene molecules, exhibit interesting electronic and structural properties due to the presence of alternating single and double bonds. There has been a recent surge in interest in studying small acenes, such as anthracene, tetracene, and pentacene. Geometry optimization and energy convergence for acene molecules are essential steps in understanding their properties and behavior. The modellings of MJs was done using Jmol computer code and the geometry of these structures was relaxed towards its minimum energy using a two-step procedures which are; pre-relax the structure with light settings and post-relaxation run using tight settings down to 10-2 eV/Å stopping criteria. The results showed that total energy uncorrected and the maximum force converged. The converged energies for anthracene, tetracene and pentacene molecules are, 0.0057 eV/Å, 0.0056 eV/Å, and 0.0060 eV/Å respectively. For the vibrational analysis, some of the results indicated that the input geometry is indeed a local minimum and not a saddle point. The results also showed a low IR absorption, with maximum intensity of 1.83 D2Å-2, 2.00 D2Å-2, and 1.91 D2Å-2 for anthracene, tetracene, and pentacene respectively.