Added masses computation for unconventional airships and aerostats through geometric shape evaluation and meshing

Abstract

The modern development in design of airships and aerostats has led to unconventional configurations quite different from the classical ellipsoidal and spherical ones. This new class of air-vehicles presents a mass-to-volume ratio that can be considered very similar to the density of the fluid displaced by the vehicle itself, and as a consequence, modeling and simulation should consider the added masses in the equations of motion. The concept of added masses deals with the inertia added to a system, since an accelerating or decelerating body moving into a fluid displaces a volume of the neighboring fluid. The aim of this paper is to provide designers with the added masses matrix for more than twenty Lighter Than Air vehicles with unconventional shapes. Starting from a CAD model of a given shape, by applying a panel-like method, its external surface is properly meshed, using triangular elements. The methodology has been validated by comparing results obtained with data available in literature for a known benchmark shape, and the inaccuracies of predictions agree with the typical precision required in conceptual design. For each configuration, a CAD model and a related added masses matrix are provided, with the purpose of assisting the practitioner in the design and flight simulation of modern airships and scientific balloons.

3‐D ballistic transport of ellipsoidal volcanic projectiles considering horizontal wind field and variable shape‐dependent drag coefficients

“…, which is in agreement with those experimentally obtained [e.g., Pantaleone and Messer, 2011;Ghassemi and Yari, 2011;Tuveri et al, 2014].…”

“…Coefficients linked to rotation about an axis in the equatorial plane have not been included since the rotation was assumed as negligible. If d = e = f , then the projectile is a sphere and , which is in agreement with those experimentally obtained [e.g., Pantaleone and Messer , ; Ghassemi and Yari , ; Tuveri et al , ].…”

Flight control of a hexa-rotor airship: Uncertainty quantification for a range of temperature and pressure conditions

“…Therefore, by replacing equation (16) into equation (15), one can obtain the dynamic equation of the rotational motion of S B w.r.t. S G :…”

“…The added-mass (also called virtual or apparent-mass) forces and torques are aerodynamic reaction efforts from a surrounding fluid on a body which tries to accelerate or decelerate inside it; note that the displaced mass of fluid is accelerated or decelerated together with the body interacting with it (see, e.g., [18,19]). This effect is only relevant if the mass of the displaced fluid is significant compared to the body's mass, which is generally the case for conventional or hybrid airships [20,9,16]. It is also worth noting that it appears even in low-speed and windless conditions.…”

“…The side effect of such inclination constraint is a low lateral acceleration capability. The second aspect is the added-mass effect [16], which consists in the reaction efforts (torque and force) of the surrounding air on the vehicle's body. It turns out that the added-mass effect causes an additional coupling between the translational and rotational dynamics, besides an apparent increasing in the vehicle's mass and inertia.…”