Hydrodynamic Characterization of Planing Surfboards Using CFD

Computational fluid dynamics is recently being considered as an interesting tool to predict and analyze surfboards’ hydrodynamic characteristics for the purpose of optimizing the design. In this paper we define a systematic methodology that could be used to measure forces and moments exerted by the fluid on the surfboard. We define a “surfboard attitude” matrix, for instance varying the angle of attack and the tip surfacing height, and we fill it with values of drag, lift and moment. With these data, we can calculate the position of the center of pressure and analyze static equilibrium conditions in the presence of external forces that represent the weight of a surfer

A FULLY IMPLICIT MATERIAL RESPONSE CODE WITH ABLATION AND PYROLYSIS FOR SIMULATION OF THERMAL PROTECTION SYSTEMS

The purpose of this paper is to introduce and describe a 2-D fully implicit numerical simulation tool capable of evaluating the behaviour of an ablative charring thermal protection system during atmospheric entry. In particular, the computational tool can model the heat transfer inside a solid porous material and the decomposition of the latter, pyrolysis gas density, pressure and speed distributions and surface recession. The governing equations are fully coupled and are integrated using a time-implicit scheme. The grid can contract to simulate the recession phenomenon and the recession rate can be evaluated using different ablation models, depending on the problem and on the available data. Spatial and temporal convergence tests demonstrated that the tool is second order accurate in space and time and comparisons with available numerical results are shown here for code verification

Detailed Modeling of Cork-Phenolic Ablators in Preparation for the Post-flight Analysis of the QARMAN Re-entry CubeSat

This work deals with the analysis of the cork P50, an ablative thermal protection material (TPM) used for the heat shield of the qarman Re-entry CubeSat. Developed for the European Space Agency (ESA) at the von Karman Institute (VKI) for Fluid Dynamics, qarman is a scientifc demonstrator for Aerothermodynamic Research. The ability to model and predict the atypical behavior of the new cork-based materials is considered a critical research topic. Therefore, this work is motivated by the need to develop a numerical model able to respond to this demand, in preparation to the post-fight analysis of qarman. This study is focused on the main thermal response phenomena of the cork P50: pyrolysis and swelling. Pyrolysis was analyzed by means of the multi-physics Computational Fluid Dynamics (CFD) code argo, developed at Cenaero. Based on a unifed fow-material solver, the Volume Averaged Navier–Stokes (VANS) equations were numerically solved to describe the interaction between a multi-species high enthalpy fow and a reactive porous medium, by means of a high-order Discontinuous Galerkin Method (DGM). Specifcally, an accurate method to compute the pyrolysis production rate was implemented. The modeling of swelling was the most ambitious task, requiring the development of a physical model accounting for this phenomenon, for the purpose of a future implementation within argo. A 1D model was proposed, mainly based on an a priori assumption on the swelling velocity and the resolution of a nonlinear advection equation, by means of a Finite Diference Method (FDM). Once developed, the model was successfully tested through a matlab code, showing that the approach is promising and thus opening the way to further developments

Wind Tunnel Testing of Remotely Piloted Aircraft Systems for Precision Crop-Spraying Applications

In recent years, precise spraying operations using Remotely Piloted Aircraft Systems (RPAS), also called drones, are growing parallel with the novel agricultural revolution. The main objective of the research activity reported in this paper is to obtain information about spray system design related to mission flight conditions. We performed a 3D scan of the reference blade geometry to allow the development of an accurate Computational Fluid Dynamics (CFD) model able to predict trajectories of droplets injected on the rotor’s wake. To validate this model, we planned and carried out a wind tunnel experimental campaign. As a result, we expect to define nozzles’ position and type along with RPAS flight velocity and altitude to achieve optimal spraying operations

Numerical Analysis and Wind Tunnel Validation of Droplet Distribution in the Wake of an Unmanned Aerial Spraying System in Forward Flight

Recent developments in agriculture mechanization have generated significant challenges towards sustainable approaches to reduce the environmental footprint and improve food quality. This paper highlights the benefits of using unmanned aerial systems (UASs) for precision spraying applications of pesticides, reducing the environmental risk and waste caused by spray drift. Several unmanned aerial spraying system (UASS) operation parameters and spray system designs are examined to define adequate configurations for specific treatments. A hexarotor DJI Matrice 600 equipped with T-Motor “15 × 5” carbon fiber blades is tested numerically using computational fluid dynamics (CFD) and experimentally in a wind tunnel. These tests assess the aerodynamic interaction between the wake of an advancing multicopter and the fine droplets generated by atomizers traditionally used in agricultural applications. The aim of this research is twofold. First, we analyze the effects of parameters such as flight speed (0, 2, and 3 m·s−1), nozzle type (hollowcone and fan), and injection pressure (2–3 bar) on spray distribution. In the second phase, we use data from the experimental campaign to validate numerical tools for the simulation of rotor–droplet interactions necessary to predict spray’s ground footprint and to plan a precise guidance algorithm to achieve on-target deposition and reduce the well-known droplet drift problem

Electromagnetic Fluid Dynamics for Aerospace Applications

Starting from the basic and general approach founded on the coupling between the Maxwell and the Navier- Stokes equations, the authors review some physical and mathematical models that are currently used in the aerospace engineering community for representing the behavior of electrically conducting flows subject to electromagnetic fields. Then, they present four different numerical methods for solving the magnetofluid dynamics equations in different formulations and for different magnetic Reynolds number regimes. For the sake of simplicity, the attention is focused on one-dimensional cases. Finally, numerical results obtained using the above mentioned numerical techniques on a magnetofluid dynamics shock-tube problem are compared and discusse