Variation Of Coefficient Research Articles

Near-moving-wall flows past three tandem elliptical cylinders at low Reynolds number of 150

Dynamic flows past three tandem elliptic cylinders of equal spacing in parallel arrangement with a moving wall are numerically conducted by the lattice Boltzmann method. The gap ratio (G/D, where G and D are the gap between the wall surface and cylinder center and major axis, respectively) from 0.6 to 2.5 and spacing ratio (L/D, where L is the distance of two adjacent cylinder centers) from 1.5 to 10 are examined at Reynolds number of Re = 150 (based on D). The desired analysis correlates variations of hydrodynamic coefficients, wake structures, and spectral analysis in wide space of G/D and L/D with underlying fluid mechanics. The flow is highly adjustable in G/D−L/D space, dividing into six distinct regimes: overshoot, continuous reattachment, alternative reattachment, wavy, meandering, and coshedding, which are spatially classified into four modes because of flow interference, namely, shear layer, primary, two-layered, and secondary vortex shedding modes. The transition between adjacent modes defines three boundaries. The first boundary always occurs behind the middle or downstream cylinder, whereas the second and third boundaries occur between the upstream and middle cylinders and the downstream cylinder wake. Due to the near-wall flow interference, the hydrodynamic coefficients are highly changeable in L/D−G/D space, signifying the crucially lower drag coefficient of the middle and downstream cylinders than that of a single cylinder. A small G/D determines the increase in lift coefficient of the upstream cylinder as a result of the ground effect, while the shadowing effect of the upstream cylinder induces identical Strouhal numbers of the middle and downstream cylinders.

Effect of hot-electron preheating on the multimode bubble-front growth of the ablative Rayleigh–Taylor instability

Hot electrons (HEs) generated via parametric instabilities at high laser intensities are a critical concern of laser-driven inertial confinement fusion (ICF), which can significantly impact the ICF performance by preheating the target. In this paper, the effects of HE preheating with moderate HE energy on the evolution of two-dimensional multimode ablative Rayleigh–Taylor instability (ARTI) up to the self-similar growth stage are studied through numerical simulations with a multigroup diffusion model. It is found that HE preheating stabilizes the linear growth of multimode ARTI and delays the onset of the self-similar growth regime. This time delay is more significant for the short-wavelength mode ARTI and higher energy HE cases. It is also shown that the variation of self-similar growth coefficients under HE preheating is not very significant. The delay to the onset of the nonlinear stage of multimode ARTI by HE preheating with moderate energy may be beneficial to ICF implosions.

Evolution of clusters of turbulent reattachment due to shear layer instability in flow past a circular cylinder

We perform large eddy simulations of flow past a circular cylinder for the Reynolds number (Re) range, 2×103≤Re≤4×105, spanning subcritical, critical, and supercritical regimes. We investigate the spanwise coherence of the flow in the critical and supercritical regimes using complex networks. In these regimes, the separated flow reattaches to the surface in a turbulent state due to the turbulence generated by the shear layer instability. In the early critical regime, the turbulent reattachment does not occur simultaneously at all span locations. It occurs incoherently along the span in clusters. We treat strong surface pressure fluctuations due to the shear layer instability as extreme events and construct time-varying spatial proximity networks where links are based on synchronization between events. This analysis unravels the underlying complex spatiotemporal dynamics by enabling the estimation of characteristics of clusters of turbulent reattachment via the concept of connected components. In the critical regime, the number and size of the clusters increase with the increase in Re. At higher Re in the supercritical regime, they coalesce to form bigger clusters, resulting in increase in spanwise coherence of turbulent reattachment. We find that the size and number of clusters govern the variation of the time-averaged coefficient of drag (C¯D) in the critical and supercritical regimes. C¯D exhibits power-law distribution with the largest cluster size (C¯D∝S¯CL−25) and the most probable cluster size [C¯D∝E(SC)−25].

Analysis of Effect of Hemodynamic Parameters on Two-layered Blood Flow in a Mild Stenosed Artery

Arterial stenosis is the lessening of the arterial wall due to the growth of aberrant tissues that prevent adequate blood flow in the human circulatory system and induces cardiovascular diseases. Mild stenosis, over time, can lead to serious and permanent damage if it remains uncured. Navier-Stokes equation in cylindrical polar coordinates system has been extended by two-layered blood flow along the axial direction with appropriate boundary conditions.A steady flow through a stenosed artery has been investigated extensively using the analytical approach in the case of two-layered blood flow. Mathematical expressions for two-layer hemodynamic parameters such as velocity profile, volumetric flow rate, and effect of stenosis progression on parameters with the variation of core and peripheral layered coefficient of viscosity are derived. Moreover, pressure drop, and shear stress have been calculated analytically in an artery with and without stenosis. Peripheral viscosity has less contribution to varying velocity distribution than the core and is proportional to stenosis size.The volumetric flow rate decreases with an increasing viscosity coefficient. Pressure drop and shear stress attain maximum value in the region stenosis occur maximum height in core layer.The present work could serve as a model in biomedical engineering for the cure of vascular-related diseases and has the potential in designing the devices of this field.

Temperature Influence on Brake Pad Friction Coefficient Modelisation.

Brake pad linings are an essential part of the correct functioning of braking systems based on the use of pads and discs. Generally, the compounds used to make the gaskets are characterised by the use of over 20 sintered components, which allow friction coefficients that vary between 0.2 and 0.6 at temperatures up to 200 °C. In this work, a traditional compound was investigated under close-to-real conditions in order to evaluate the tribological behaviour at different temperatures. Finally, a model based on the proportionality between temperature increase and relative variation of the friction coefficient was proposed. From the experimental test, it was evident that the friction coefficient increased with the temperature, passing from 0.4 to 0.6 in the temperature range of 100 °C to 180 °C; however, a further temperature increment until 350 °C caused a reduction in the friction coefficient to 0.2. The proposed model was able to anticipate the abovementioned trend, especially at high temperatures.

Optimal conversion coefficient from easily measurable dose to effective dose with consideration to radiation quality for posterior–anterior chest radiography

Effective dose is sometimes used to compare medical radiation exposure to patients and natural radiation for providing explanations about radiation exposure to patients, but its calculation is lengthy and requires dedicated measuring devices. The purpose of this study was to identify the most suitable conversion coefficient for conversion of easily measurable dose to effective dose in posterior–anterior chest radiography, and to evaluate its accuracy by direct measurement. We constructed an examination environment using Monte Carlo simulation, and evaluated the variation in conversion coefficients from incident air kerma (IAK), entrance-surface air kerma (ESAK), and air kerma-area product (KAP) to effective dose when the irradiation field size and radiation quality were changed. Effective doses were also measured directly using thermoluminescence dosimeters and compared with the effective dose obtained from conversion coefficients. The KAP conversion coefficient most effectively suppressed the effect of irradiation field size, and was then used to set conversion coefficients for various half-value layers. The optimal conversion coefficient was 0.00023 [mSv/(mGy·cm2)] at 120 kVp (half-value layer = 5.5 mmAl). Evaluation of the direct measurements obtained with various radiation qualities revealed that the accuracy of the conversion coefficient was maintained at ≤ 11%. The proposed conversion coefficient can be easily calculated even in facilities that do not have equipment for measuring effective dose, and might enable the use of effective dose for providing explanations about radiation exposure to patients.

Investigation of the aerodynamic effects of bio-inspired modifications on airfoil at low Reynolds number

A numerical study was performed to investigate flow behaviors around bio-inspired modified airfoils compared with NACA 4412 airfoil at Re=5.8x104 by solving the two-dimensional, RANS equations with k-ω STT turbulence model. The obtained results reveal a rather abrupt decrease of lift at stall for the NACA 4412 airfoil in contrast to the mild stall depicted by the top-modified airfoil. As compared to the experimental results of the profiled airfoil in the literature, the characteristic behavior of the variation in the lift coefficient shows resemblance. It is seen that from the velocity distribution results, fluid flowed smoothly along the streamlined nose of NACA 4412 airfoil until α=4⁰ and streamlines adhered well for both airfoils at low angles (0⁰, 2⁰). Smaller circulation bubbles were noticed to settle in the canyons of the corrugated cross-section of the top-modified airfoil. In the wake region of the modified airfoil, there is no obvious large flow separation or circulation region at low angles of attack. However, the blue regions of the dimensionless velocity over the NACA 4412 airfoil and bottom-modified airfoil were narrower than over the top-modified airfoil. The recirculation zone over the airfoil started to enlarge, and the rolling up of the trailing-edge vortex appeared. After α=12⁰, the adverse pressure gradient on the suction side of the airfoils became more intense. In the wake zones, it was seen that the circulation regions grew remarkably and became largest as the angle of attack rose to α=16⁰, which pointed out increased drag forces of airfoils.

New accelerated rock creep model considering nonstationary viscosity coefficient

Accelerated creep models are popular research topics in rock mechanics. By analyzing the variation in the viscosity coefficient in the accelerated creep stage and defining the viscoplastic internal variable, a general evolution law for the viscosity coefficient was revealed, and a widely applicable accelerated creep model was proposed. First, the creep test data of 24 rock types were collected and analyzed. Subsequently, the contrast between the strength decrease in the accelerated creep-subsequent failure stage and the post-peak strength decrease in the elastoplastic process was evaluated, and the viscoplastic internal variable in the accelerated creep stage was defined. Subsequently, the evolution function between the normalized viscosity coefficient and the viscoplastic internal variable was established. Based on the test data for different rocks, the predicted curves accurately captured the evolution of the normalized viscosity coefficient with the viscoplastic strain increment and confining pressure in the accelerated creep stage. A new accelerated creep model was constructed by modifying the linear viscoplastic part of the Nishihara model using an established evolution model of the viscosity coefficient. The model demonstrated agreement with the experimental data for different rocks and yielded results close to the monitored tunnel convergence data.

Coupled model on the variation of diffusion coefficient and surface chloride concentration in reinforced concrete structures over time

Durability analyses and service life estimates of structures in a marine environment can be developed through the modeling of chloride concentration profiles. However, as surface chloride concentration and diffusion coefficient vary over time, especially due to the cement hydration process, modeling chloride profiles from structures with recent degradation ages requires an adjustment for the temporal dependence of these two physical parameters. The variation of the surface chloride concentration (Cs) as a function of time tends to show an increasing asymptotic behavior, while the diffusion coefficient (D) has a decreasing asymptotic tendency. For this reason, the power function, usually used to describe the diffusion coefficient, has problems for advanced ages, while the exponential function has difficulties at recent ages. Therefore, the key issue in this problem is the rate of change of Cs and D over time. This article presents the development of a single time-dependence model to simultaneously describe the decrease in D and the increase in Cs over time. The coupled model is a piecewise-defined function, with continuity of the function and its first derivative in the transition time between recent ages and more advanced ages, defined as 10 years. To validate the new model, data from structures under natural degradation were used. The results demonstrated the applicability of the coupled model with individual adjustments of the exponent α, which implicitly represents material properties and environmental parameters. However, in the absence of sufficient information, a standard α exponent of 0.25 per year can be adopted, demonstrating a moderate to strong adherence of the coupled model to the Cs and D data over time. Three stages of temporal dependence were identified: I – up to 10 years: marked increase in Cs and decrease in D over time; II – between 10 and 25 years: decrease in the variation rate of Cs and D; and III – from 25 years: stabilization of Cs and D.

Global adaptive neural network control of nonlinear time-varying systems with unknown control coefficients and model uncertainties

This paper investigates the adaptive control problem for the strict-feedback nonlinear time-varying system (NTVS) with unknown control coefficients and model uncertainties. To address the problem that the neural network (NN) can only achieve local approximation of unknown nonlinear functions, a novel NN control scheme is proposed. The scheme consists of a NN controller that operates inside the approximation domain and a robust controller that operates outside the approximation domain, and a novel switching function is designed to enable the two controllers to switch smoothly in the vicinity of the approximation domain to ensure that all signals of the closed-loop system are globally uniformly ultimately bounded. To address the problem that unknown time-varying control coefficients are difficult to handle, an adaptive fault-tolerant control scheme is proposed in combination with the congelation of variables method. The scheme employs classical adaptive control to adapt to the variation of unknown control coefficients and robust control to eliminate the time-varying disturbance terms, and introduces a positive integrable time-varying function to achieve asymptotic tracking of an arbitrary reference signal. The combination of these two schemes constitutes a global adaptive neural network control (GANNC) method for the NTVS with unknown control coefficients and model uncertainties. Finally, an adaptive attitude fault-tolerant controller for launch vehicles is designed by using the GANNC method, which can realize the accurate tracking of the attitude control system to the reference command under normal status, strong disturbances and actuator failures, and comparative experiments prove the effectiveness and superiority of the controller.

Experimental investigation on influence of terrain complexity for wind pressure of low-rise building

This study conducted extensive wind tunnel tests to evaluate the impact of terrain complexity on wind pressure across low-rise buildings. A series of wind tunnel tests was performed using 50 actual terrain morphologies in the US. The findings were compared with results obtained from testing on homogeneous terrain to discern variations in pressure coefficients. A notable increase in turbulence intensity was observed in complex heterogeneous terrains, even with similar effective roughness lengths. The heightened turbulence property was a crucial factor in explaining changes in Cp,mean. The magnitude of Cp,mean demonstrated a continuous rise in the windward wall and roof 1 regions with increasing turbulence intensity. This correlation held true even for Iu,eave values surpassing 0.3. In contrast, while Cp,RMS exhibited a tendency to increase with rising Iu,eave, it did not exhibit the same continuous increase phenomenon. Consequently, no significant disparity in magnitude was noted between homogeneous and heterogeneous terrains in this regard. These findings underscore the importance of accounting for terrain complexity in wind load assessments, particularly in scenarios of heightened terrain diversity, to mitigate potential errors in wind load evaluations.

A novel VP1-based enzyme-linked immunosorbent assay revealed widespread Enterovirus G infections in Guangxi, China

Enterovirus G (EV-G) has recently been shown to affect weight gain and cause neurological symptoms in piglets. However, the serological investigation of EV-G is limited. In this study, we developed a novel serological detection method based on the structural protein, VP1 of EV-G. The intra-assay and inter-assay coefficient variations were 3.2–8.9% and 2.6–8.0%, respectively. There was no cross-reaction of the VP1-based enzyme-linked immunosorbent assay (ELISA) with antisera against the other known porcine viruses. In addition, a comparison was made with other methods including the developed indirect ELISAs based on VP2 and VP3 proteins and western blot (WB) analysis, which demonstrated the reliability of the novel method. Using the VP1-based ELISA, we carried out the first seroepidemiological survey of EV-G in China by testing 1041 serum samples collected from different pig farms in Guangxi from 2019 to 2021. Our results showed that 68.78% of the serum samples and 100% of the pig farms were positive for EV-G, with a relatively high incidence of seropositivity in pigs of different ages. This was specifically evident in fattening pigs and sows, which may suggest that the piglets have experienced an infection with EV-G during their growth process. Our data provide the first serological evidence of EV-G infections in pigs from China and reveal the widespread presence of EV-G infections in Guangxi, China.

A new similarity criterion for wind tunnel testing of floating wind turbines achieving dynamic aerodynamic characteristics similarity

Floating offshore wind turbines have rapidly advanced in recent years, prompting numerous experiments. Small-scale turbines require blade redesign with low Reynolds number airfoils due to the scale effect. Consequently, the chord length of these blades no longer corresponds to the length scale, leading to dissimilar dynamic aerodynamic phenomena during platform movement. To address this, a new criterion is proposed for wind tunnel tests of floating offshore wind turbines. The criterion incorporates reduced frequency correction and optimal tip speed ratio (TSR) matching. It ensures hydrodynamic similarity through Froude number similarity and avoids excessive low wind speed through wind speed correction. Optimal TSR matching ensures the model and prototype turbines operate within similar power curve intervals. Reduced frequency corrects the platform sine motion parameters, providing the model turbine with a dynamic aerodynamic effect similar to the prototype. The National Renewable Energy Laboratory’s 5 MW wind turbine is chosen as the prototype, and the model wind turbine blades are designed using NACA 4412 airfoil and the criterion of thrust coefficient similarity. The sub-module of the FAST, AeroDyn is employed to validate the new criterion for different surge motions between the NREL 5 MW and the model. Under the new similarity criterion, the model turbine exhibits a relative root mean square error of 4.61 % and 1.54 % in power coefficient and thrust coefficient, a significant improvement compared to the current similarity criterion's relative root mean square error of 24.74 % and 8.36 %. The results reveal a circular trend variation in both thrust coefficient and power coefficient with position. Notably, the new criterion demonstrates a closer alignment with the dynamic aerodynamic characteristics of the prototype when contrasted with the current similarity criterion. Furthermore, this model design, tailored for the NREL 5 MW turbine, can be applied to model experiments with various turbine configurations. It has been successfully verified for the IEA 15 MW turbine, exhibiting promising simulation results. The proposed similarity criterion is suitable for wind tunnel testing, addressing the problem that the current similarity criterion cannot reflect the dynamic aerodynamic characteristics of prototype wind turbines. Additionally, it enables experiments on different prototype configurations using a single model turbine, reducing wind tunnel testing costs.

Development and application of the UVC LED-based spectrophotometer for high frequency online monitoring of nitrate concentration in municipal wastewater

Developing a fast, sensitive and stable sensor for online monitoring nitrate concentration is an urgent need for the optimization of denitrification processes in wastewater treatment plants (WWTPs). In this study, the miniaturized spectrophotometric nitrate sensor was developed using UVC light-emitting diodes (LEDs) coupled with AlGaN or SiC-based photodiodes. The use of novel SiC photodiodes could effectively eliminate UVB and UVA light in the 230 nm LED emission spectra. Replacing 235 nm UVC-LED with 230 nm UVC-LED could effectively increase the detection sensitivity but not the linear range that follows the Lambert-Beer's law. The influences of dissolved organic matter (DOM) on nitrate analysis could be corrected by a unified coefficient α across the NO3--N concentration ranging in 0–50 mg/L. Across the investigated WWTP samples, the correction coefficient α was mainly determined by the fractions of humic substances with apparent molecular weight (MW) of 1.5–9.0 kDa, while the degradation of the large MW proteinaceous biopolymer resulted in dramatic variations of correction coefficient α along the WWTP A/A/O process. Microfiltration membranes with pore sizes ≤ 30 µm could sufficiently eliminate the influences of particles in effluents on photometric nitrate analysis. The ultrafiltration and enhanced coagulation treatment could effectively remove the biopolymer fractions of DOM in wastewater, and thus alleviate its influences on sensitivity and accuracy of nitrate analysis. The spectrophotometric nitrate sensors were successfully applied for on-line monitoring NO3--N concentrations in the influent and effluent of denitrifying biofilter in a municipal WWTP, providing high-frequency feedback signals to precise control of feeding external carbon source.

Radiation shielding properties of some igneous rocks in isparta province at different gamma energies: Experimental and theoretical study

In this study, our aim is to experimentally and theoretically obtain the gamma radiation shielding properties of some igneous rocks extracted in Isparta, Turkey. In the first stage, experimental measurements were performed using a gamma spectroscopy system containing a NaI(Tl) detector at three different gamma energies (511, 835 and 1275 keV) emitted from two different radioactive sources (22Na and 54Mn). As a result of the experiments, linear attenuation coefficients (LACs) of igneous rocks were obtained. The variation of LAC was investigated in relation to the density and the alkali-silica content of the rocks. The results obtained indicated an increase in the LACs with higher rock and an elevated alkali-silica ratio. Using the experimental LAC results, the half and tenth value layer thickness (HVL and TVL), mean free path (MFP), transmission rate, radiation protection efficiency (RPE) and lead equivalent thickness (dPb) values were calculated. In the second stage of this study, LACs were calculated theoretically with the help of XCOM software using the chemical contents of the selected igneous rocks. The comparison of experimentally obtained LACs with those calculated using the XCOM software, revealed a good agreement between the two methods. In addition, the results obtained with the XCOM software gave information about the variation of the attenuation coefficient in different energy regions. Moreover, effective atomic number (Zeff) and electron density (Ne) parameters were calculated using XCOM and experimental results. Based on the data collected, it can be concluded that the trachy-basalt sample taken from the igneous rocks used in this study is more effective than other rocks in terms of gamma radiation shielding.

Effect of colemanite mineral on gamma radiation attenuation properties of vinyl ester resin

In this study, it is aimed to experimentally and theoretically obtain the gamma radiation attenuation properties of vinyl ester resin (VE) containing different rates of colemanite (CO) mineral and to compare these results. In the first stage, experimental measurements were performed using a gamma spectroscopy system containing a NaI(Tl) detector at three different gamma energies (511, 835 and 1275 keV) emitted from two different radioactive sources (22Na and 54Mn). As a result of the experiments, linear attenuation coefficients (LACs) of VE samples were obtained. The variation of LACs according to the density of the samples were investigated. The obtained results showed that LACs increased the density of the VE samples increased. Using the experimental LAC results, the half (HVL) and tenth (TVL) value layer thickness, mean free path (MFP) and transmission rate values were calculated. In the second stage of the study, LACs were calculated theoretically with the help of XCOM code using the chemical contents of VE samples. As a result of the comparison of the LACs obtained experimentally and using the XCOM code, it was observed that they were in good agreement. In addition, the results obtained with the XCOM code gave information about the variation of the attenuation coefficient in different energy regions. Based on all these data, it was concluded that as the amount of colemanite in the vinyl ester resin examined in the study increased, the gamma radiation shielding performance increased.

On the structural stability for a model of mixture of porous solids

The present paper is dedicated to the structural stability of the linear model of a mixture of two porous solids. It is shown that the variation of the characteristic coefficients that describe the coupling of the various mechanical effects involved in the model in concern does not destroy its structure. This means that any small variation of these coefficients leads to small variations in the corresponding solutions of the associated initial boundary value problems. For this purpose, more mathematical estimates are presented describing precisely the continuous dependence of the solutions with respect to all external given data of the initial boundary value problem, as well as with respect to appropriate measures of the set of coupling parameters. This allows the conclusion that the model of the mixture of porous materials is consistent. In particular, it is believed that the estimates obtained in terms of structural stability are particularly meaningful with regard to the materials used in building contexts and the related decay phenomena.

RESEARCH ON AERODYNAMIC NOISE CHARACTERISTICS OF HELICOPTER ROTORS CONSIDERING THE INFLUENCE OF BLADE SHAPES

In this study, we investigated the influence of blade shapes on the aerodynamic noise characteristics of helicopter main rotors by the vortex method. The obtained results are the variation of the time-dependent lift coefficient of rotors and the aerodynamic noise characteristics of the helicopter rotor with different blade shapes. On that basis, the influence of the blade shape on the aerodynamic noise characteristics of helicopter rotors was evaluated. An advanced blade shape was designed to reduce the aerodynamic noise of rotors while maintaining the lift of the rotor. Computational results show that the rotor with the advanced blade generates the lower noise, and the noise of the advanced blade reduces by up to 6.15 dB (reduced by 6.90%) compared with the common rectangular blade in hover and up to 5.4 dB (reduced by 5.15%) in forward flight.

User verification of Abbott Alinity HQ hematology analyzer

Abstract Objectives This study aims to evaluate the performance characteristics of the Alinity HQ hematology analyzer in a routine laboratory setting. Methods In the study, precision (short-term and long-term precision), accuracy (method comparison with Abbott Cell Dyn Ruby and estimation of bias), confirmation of a background (Limit of Blank, LoB), and carry-over were used to evaluate the performance of Alinity HQ as recommended by ICSH, CLSI guidelines EP15-A3, EP09, EP17A2, and H26-A2. Acceptance criteria were based on manufacturer technical specifications and the EFLM Biological Variation Database. Results According to the short-term precision results, except for mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC), all measurements exhibited coefficient variations (CV) lower than their verification limits. Basophil, eosinophil, and monocyte counts, as well as mean corpuscular hemoglobin (MCH), MCHC, and red cell distribution width standard deviation (RDW-SD), did not meet the allowable imprecision criteria for the long-term precision study. The estimated bias for all analytes was within verification limits. However, the method comparison study showed concentration-dependent variations for MCHC, MCH, and mean platelet volume (MPV) parameters. Furthermore, the correlation of parameters between Alinity HQ and Cell Dyn Ruby ranged from 0.46 to 1.00. The LoB and carry-over studies demonstrated satisfactory performance for the Alinity HQ analyzer. Conclusions Although some parameters had higher CVs than expected and concentration-dependent bias, the overall analytical performance of Alinity HQ was found to be satisfactory. Alinity HQ is an accurate, highly precise analyzer with good analytical performance, suitable for high-volume laboratories.

The effect of characteristics of the mold with and without pin fins on the cooling profile in rotomolding sistem by FEM

In the rotomolding processes, the cooling stage is important, which affects significantly the productivity and quality of the final product. Therefore, in this work, a computer simulation was performed, studying the effect of the pin fins on the mold in the cooling phase in the rotomolding system, thus, steel and aluminum molds with and without pin fins were considered. In this work we had the following results, according to the optimization process, due to the high conductivity and low density of aluminum, it was verified that less pin fins were needed around the mold aluminum than for steel, but the length of the pin fins was greater for aluminum; in addition, the mold with fins had a faster cooling than the mold without fins; meanwhile, the use of appropriately sized fins significantly reduces the cooling time, nevertheless, as has been observed that the increasing or decreasing the fin number, the cooling profile is very little affected. However, the variation of the conviction coefficient applied to the external surfaces was also investigated, but the behavior of the fins are more efficient when the convection coefficient is higher so improving productivity. Finally, he characteristic of the mold material was also examined, as the steel mold with fins has a sharper cooling compared to the same material without fins, however, the aluminum was more efficient, because the cooling process was faster in molds of aluminum with fins. Emphasizing, the numerical simulation can be satisfactorily applied in the industrial process of rotomolding, of a simplified manner and qualitatively, promoting growth in production and reducing so the costs considerably associated with the production.