Fruit packaging is highly impactful in temperature and humidity distribution for post-harvest fresh fruit cooling and conservation. It is also the most flexible part on fruit production and should be able to increase shelf-life by deterring adverse conditions. However, packaging thermal performance during cold storage where it is displayed to the internal airflow is influenced by the size and position of vent-holes. In this study airflow inside the fruit box and fruits thermal behaviour are evaluated in order to determine differences between three prototype package models. Models differ from each other by the holes' configuration and size. Furthermore, models' performance is compared to a commercially available box of similar dimensions. Experimental tests were carried out in three stacked boxes, equipped with temperature and humidity sensors, and placed inside a refrigeration chamber with forced air cooling. Packaging box CFD models of each prototype wall were developed to predict the airflow and heat transfer during storage in a refrigeration chamber. Models predictions were validated by experiments results. According with simulation results, all prototypes have better thermal performance than the commercial model. However, significant performance differences between prototype walls were found. Fewer, larger and strategically distributed vent-holes allow a better result in terms of temperature homogeneity inside the box and significant reduction in fruit cooling times.

Nowadays, the advances in computer hardware and software allowed the development of a new generation of Computational Fluid Dynamics (CFD) codes which are much more user-friendly in terms of mathematical modelling, numerical techniques and presentation of results. The aim of this study is to present the evaluation and comparison between the numerical results obtained with two commercial codes, an academic one and experimental data for a of a typical ventilation case study. Therefore, the scope includes the validation of the numerical results and discussion of the potentialities, complexity and user interface of each code.

This study performs a Computational Fluid Dynamics (CFD) modeling of air flow and heat transfer of an open refrigerated display cabinet in order to evaluate the influence of the discharge air velocity on the performance of its recirculated air curtain. The physical-mathematical model considers the flow through the internal ducts, across the fans and the evaporator, and also the thermal response of food products. The fan boundary condition is modeled in order to vary the air velocity at the discharge grille. The back panel perforation is modeled as a porous medium. The density and dimension of the back panel perforation variation is modeled by the Darcy's law with the Forchheimer extension, varying the viscous and inertial resistance coefficients of the porous medium, based on its porosity, permeability, air velocity and pressure loss coefficient. Experimental tests were conducted to characterize the phenomena near the physical borders and to prescribe boundary conditions as well as to validate the numerical predictions on the temperature, relative humidity and velocity distributions.

Experimental studies in building energy usage and environmental analysis are very time consuming and expensive, and require sophisticated sensors and instrumentation techniques. So, there has been great interest in developing Computational Fluid Dynamics (CFD) computer codes to improve building design and HVAC systems. The majority of these CFD programs are based on the solution of Navier-Stokes equations, the energy equation, the mass and concentration equations as well as the transport equations for turbulent velocity and its scale. The aim of this study is to present the advantages, applicability and potentialities of CFD in building design. The advantages and the performance of (two) commercial CFD codes and an academic CFD code develop for this purpose are evaluated. The codes were applied to predict typical situations of the airflow in buildings and the predictions were compared with experimental results.

Maritime Unmanned Vehicles are tools being developed to explore oceans, rivers, lakes and reservoirs. These tools are essential to completely understand the unknown maritime world, since they have relatively low operation costs and can perform several multipurpose investigations. These main applications can be divided in different operations types like oceanographic and atmosphere measurements. One type of these tools are called Autonomous Surface Vehicles (ASV), which, as the name implies, are autonomous vessels that operate at water’s surface. In this dissertation, different types of geometries for a next-generation bathymetric ASV are studied. The first two are more conventional geometries with the first being a flat bottom hull, and the second being a hybrid one. The last one is a new type that has recently gained recognition: a Small-Waterplane-Area Twin-Hull (SWATH) geometry. This one, consists of an axisymmetric body, two small arms that separates the body from the payload, an elliptical nose and a conical tail. All geometries have been designed taking into account the best ranges of empirical/analytical relations, previously studied by other authors. [...]

The purpose of the present work is to describe the ability of the advanced computer packages (CFD codes) to perform numerical simulations of general refrigeration engineering problems. The case study concerns the modelling of three-dimensional turbulent airflow with thermal buoyant effects and air temperature distribution in the refrigerated compartment of a perishable foodstuff transportation vehicle. The numerical predictions obtained with three commercial codes (PHOENICS, FLUENT and CFX) and an academic one are evaluated and compared with experimental data. The validation of the numerical results is analysed and the modelling capabilities, usage simplicity and user interface of each code are discussed.

The present study focuses on investigating the aerodynamical interaction between a threeelement wing and wheel in ground effect, regarding the Formula One regulations change set for 2022 - amongst the changes is the declutter of the front wing, consequently reducing its complexity. This was accomplished by conducting a three-dimensional computational analysis, using a Detached Eddy Simulation approach, on a simplified one-quarter CAD model, built from the ground up following the regulations imposed by the FIA. The main goal was to examine how changing the front wing pressure distribution affected wheel aerodynamics, which will then influence the feeding process of the underbody, due to their proximity and subsequent flow interaction. This was done by varying the angle of attack of the second flap on the wing. The CFD study was divided into two sections: a flow analysis and a force analysis. On the flow analysis, one focused on determining the location and intensity of flow energy losses; visualizing the flow structures around the wing and wheel; and, where possible, identifying and comprehending the mechanisms behind the observed flow phenomena. On the force analysis, the transient variations of the force coefficients were examined to better understand how the unsteadiness of the vortices influenced the wing’s performance. The flow investigation indicated that the wheel wake structure is significantly influenced by the wing’s flap configuration, showing different shapes to the different geometries tested. This is mainly due to the fact that different flap configurations produce different upwash flow fields, leading to a separation point variation on top of the wheel. This variation then affects the downwash observed behind the central region of the wheel, for a vertical plane. The force investigation showed that the location of the region of instability influences the behaviour of the transient oscillations, regarding the forces acting on the wing: bearing in mind that vortex breakdown occurs near the wing’s trailing edge, higher drag force fluctuations are detected, when compared to downforce fluctuations – a shared pattern across the geometries tested.

Unsteady aerodynamics is the study of flows that pass an object subjected to oscillations, which has a strong association with bioinspired flows and rotor dynamics. The central objective of the paper is to study the propulsive characteristics of two plates at a Reynolds number of 3.1x10^3 with straight and sharp trailing edges. The reduced frequency is kept between 1.0 and 5.0 with a nondimensional amplitude ranging between 0.125 and 0.500. The problem was solved numerically using CFD (Computational Fluid Dynamics), and results show that differently from what is usually observed in airfoils, the mean thrust coefficient does not increase monotonously with the reduced frequency, having a dip around k = 3.0. The same is not verified for the mean power coefficient, which increases continuously with the reduced frequency. Two phenomenon responsible for the reduction of the mean thrust coefficient is identified. Through analysis of pressure contours around the flat plates, a low-pressure zone was seen near the trailing edge, creating a suction effect in that zone. The influence of k on the formation of the LEV is analyzed, via its approximate radius, evidencing a behavior similar to the mean Ct . Furthermore, the trailing-edge shape revealed to be an important factor on thrust reduction.

The processing efficacy and energy efficiency of data centers (DC) is directly related with the cooling performance of the air-conditioning systems. The cooling effectiveness depends on airflow pattern and temperature distribution. This paper presents the parametric study of three-dimensional (3D) computational fluid dynamics (CFD) models to improve these technical characteristics. In this case study the most suitable thermal load, as deemed by the organization, of the heat flow boundary condition is simulated and studied for maximum and minimum airflow. The analysis of the numerical results provides a prediction of the thermal performance, i.e., the lower values and spatial gradients (hot spots) of air temperature and velocity while maintaining the computational processing requirements. These results allow the development of an optimized CFD model for setting up the operational parameters of CRAC systems for DC rooms.

The recent increase in interest in artificial intelligence and neural networks has stirred up various industries. Inevitably, its application will trickle down to the most fundamental studies, for instance, unsteady aerodynamics. The present paper serves the purpose of exploring the ability of a recurrent neural network to predict flapping airfoil aerodynamics, in particular the lift coefficient of a plunging NACA0012 airfoil. Thus, a neural network is designed and trained using motion parameters, such as motion frequency and effective angle of attack, to output the instantaneous lift coefficient over a plunging period. Training data is generated using a panel code (HSPM) for fast generation and early testing. Results show that the neural network can adequately predict the lift coefficient for various conditions, including plunging kinematics that are far from the training domain. Future work will build on this framework and extend it to other aerodynamic coefficients using CFD results and experiments, which should enhance the value of the estimates.