Liquid Payloads Research Articles

Modeling the effect of liquid movement on the center of gravity calculation of agricultural vehicles

Due to a high center of gravity (CG) location, agricultural vehicles are more vulnerable to overturns. The CG location can be calculated using the lifting axle method of ISO 16231-2:2015. But, as a vehicle is lifted, its liquid payloads are not entirely contained. The liquids will shift both in position and form, affecting the CG height calculation.A mathematical model was developed to predict the effect of liquid movement on the CG height calculation of a tilted vehicle. The model was validated using an agricultural utility tractor and a prototype. The developed model was applied to calculate the CG location considering the effect of the liquid shift.Results showed tilting produced a higher calculated center of gravity due to liquid movement, but by increasing the tilting angle, the calculated CG height decreased. The effect of the liquid shift on CG height measurement for the wagon with 16.0% liquid mass was 14.8% and for the tractor with 1.2% liquid mass was 0.41%. The model error was less than 1.3% for all tests. Considering the effect of the liquid shift in CG height calculation, the error in CG height calculation decreased from 11.9% to 2.6% for the wagon.

ECT imaging and CFD simulation of different cyclic modulation strategies for the catalytic abatement of hazardous liquid pollutants in trickle-bed reactors

Aiming to accomplish stringent regulations for the secure disposal of hazardous compounds, trickle beds have been envisaged from a process intensification point of view to adhere to environmental guidelines. In this work, several experimental and computational runs were performed under reacting flow conditions and cyclic (flow rate) modulations for the mineralization of liquid pollutants through electrical capacitance tomography (ECT) and computational fluid dynamics (CFD) techniques, respectively. First, we have investigated the hydrodynamics of propagating liquid pulsations generated via ON–OFF liquid, ON–OFF gas, and gas/liquid alternating cyclic operations. Here, the liquid pulsation intensity generated in ON–OFF gas mode indicated a negligible dependence with respect to cycle frequency apart from being qualitatively analogous with respect to ON–OFF liquid mode. Second, the effect of oxidation temperature and the gas and liquid flow rates unveiled the gas/liquid alternating mode as being able to generate sizable liquid payloads interrupted by gas and liquid streams. Correspondingly, we found higher detoxification rates due to the periodic pulsations sustained down to the reactor outlet by conferring improved catalyst wetting efficiencies. Finally, two-dimensional mappings of different cross-sections allowed inferring by means of ECT and CFD how the liquid payloads were morphologically in disposition to preserve or dissipate their original structure.

Trajectory Prediction of Spin-Stabilized Projectiles with a Liquid Payload

Abstract : Payloads that behave like a liquid are carried on board some projectile configurations, and it is well established that the internal motion of a liquid payload can induce destabilizing moments on the projectile. This report creates a method to include the effect of a liquid payload in the flight dynamic equations of motion, enabling trajectory simulations of projectiles with liquid payloads. To include this effect, liquid payload moments are added to the applied loads on the projectile. These loads are computed by solving the linearized Navier-Stokes equations for a projectile undergoing coning motion. To highlight the methodology, trajectory simulation results are provided for an example projectile with different liquid payload configurations possessing stable behavior while one exhibits catastrophic flight instability.

Experimental Validation of a Coupled Fluid-Multibody Dynamics Model for Tanker Trucks

Abstract : A time-accurate finite element model for predicting the coupled dynamic response of tanker trucks and their liquid payloads is presented along with an experimental validation of the model. The tanker truck components are modeled using rigid bodies, flexible bodies, joints and actuators. The model is validated using a full-scale army heavy class tactical trailer carrying a water tank. The trailer is placed on an n-post motion base simulator which was used to perform harmonic/ramp pitch, roll and stir excitations of the trailer in order to simulate typical road maneuvers. Experiments were carried out with an empty tank and a 65%-filled tank. The time-histories of the tires and suspension system deflections are measured for the various input motion excitations. The experiment's measurements are compared with the results predicted using the computational model. The comparison shows that the model can predict with reasonably good accuracy the test tanker-trailer's dynamic response.

Resonance phenomena in viscous fluids inside partially filled spinning and nutating cylinders

Spin-stabilized projectiles with liquid payloads may experience different types of flight instabilities caused by the fluid motion in the payload cylinder. The first type is known to occur in low-viscosity fluids, i.e., at high Reynolds numbers, owing to resonance with inertial waves at critical frequencies. The second type originates from a forced secondary flow at arbitrary frequency, and is most pronounced for fluids of high viscosity, i.e., relatively low Reynolds numbers. For cylinders completely filled with a single fluid, these instabilities were analyzed by eigenfunction expansion developed by Selmi, Li, and Herbert [Phys. Fluids A 4, 1998 (1992)]. The method permits unified analysis of both types of instability, since it can be used for flows at moderate as well as high Reynolds numbers. Often in practice, cylinders are made to include a central rod to alter resonance properties or are partially filled during production, to ensure safety as the liquid payload may expand under different conditions. In this paper, the eigenfunction approach is extended to analyze the moments caused by the flow in a spinning and nutating cylinder, containing a partial fill or a central rod. The analysis shows that the fill ratio (defined as the ratio of the volume of the fluid to the volume of the cylinder) affects resonance with inertial waves. The inviscid flow equations are solved analytically to provide criteria for the onset of resonance in the two configurations.

Eigenfunction expansion of the flow in a spinning and nutating cylinder

Spin-stabilized projectiles with liquid payloads may experience different types of flight instabilities caused by the fluid motion in the payload cylinder. The first type is known to occur in low viscosity fluids, i.e., at high Reynolds numbers owing to resonance with inertial waves at critical frequencies. The second type originates from a forced secondary flow at arbitrary frequency and is most pronounced for fluids of high viscosity, i.e., relatively low Reynolds numbers. In this paper a method is developed that permits unified analysis of both types of instability since it can be used for flows at high Reynolds numbers inaccessible to other approaches. The method is based on a spatial eigenfunction expansion of the axial velocity component and reduces the three-dimensional problem to one dimension. The eigenfunctions are given in closed form and the eigenvalues are determined numerically by solving a system of nonlinear equations.

Low Reynolds number Navier-Stokes simulation for rotating liquid-filled containers

Three-dimensional, steady, laminar, incompressible Navier-Stokes equations are solved using an implicit finite-difference scheme based on successive over-relaxation. These low Reynolds number numerical simulations are used to predict the behavior of liquids undergoing steady spin and steady precession at a fixed precession angle. Low Reynolds number simulations are applicable to slowly spinning vehicles or highly viscous liquid payloads. The liquid is contained in a fully filled axisymmetric container; the particular geometry examined in this paper is a right-circular cylinder with flat or rounded endcaps. Numerical predictions of viscous and pressure moments due to the liquid fill at low Reynolds number are reported. These moments tend to increase the precession angle and reduce the spin rate of the container. Liquid-induced roll and side (yaw) moments are computed as functions of endcap height to cylinder radius (0 < e/a < 1), cylinder half-height to radius (0.5 < c/ a < 4), Reynolds number (20 < Re < 3 X 102), ratio of precession to spin rate (0.05 < r < 0.95), and precession angle (ac = 2 deg). For a given cylinder, rounded endcaps can decrease the resonant liquid-induced moment by about 20% and shift the resonance to a smaller Reynolds number (for fixed precessional frequency). Thus, rounded endcaps can produce flight stability for some projectiles with highly viscous liquid payloads.

Viscous fluid motion in a spinning and nutating cylinder

Abstract : Spin-stabilized projectiles with liquid payloads can experience a severe flight instability characterized by a rapid yaw-angle growth and a simultaneous loss in spin rate. Laboratory experiments and field tests have shown that this instability originates from the internal fluid motion in the range of high viscosity. After evaluation of the experimental data and analysis of the equations for the fluid motion in a spinning and nutating cylinder, we have developed a simple model of this flow. Disregarding the finite length of the cylinder, this model provides the flow field and the viscous contribution to the liquid moments in analytical form. At low Reynolds number, the flow field agrees well with computational results for the center section of a cylinder of aspect ratio 4.3. The roll moment caused by this flow largely agrees with experimental data for a wide range of reynolds numbers. Estimates of the temperature variation indicate that discrepancies at very low Reynolds numbers may originate from associated changes of the viscosity during the experiments. The flow in an infinitely long cylinder has been utilized as a basic flow subject to axially periodic cellular disturbances. Both, the inviscid and the viscous situations have been studied. Parametric excitation of the cellular motions has been found at low Reynolds numbers. A small experiment has been designed to visualize this cellular motion in a finite-length cylinder.

Flight trajectory simulation of fluid payload projectiles

A flight trajectory simulation method has been developed for calculating the six degree of freedom motion of fluid filled projectiles. Numerically calculated internal fluid moments and experimentally known aerodynamic forces and moments are coupled to the projectile motion. Comparisons of predicted results with flight test data of an M483 155mm artillery projectile with a highly viscous payload confirm the accuracy of the simulation. This simulation clearly shows that the flight instability is due to the growth of the nutation component of angular motion caused by the viscous effects of the fluid payload. This simulation procedure, when used in conjunction with the previously developed method for calculating internal fluid moments, allows the designer to examine the effects of various liquid payloads and container geometries on the dynamic behavior of flight vehicles.

A relation between liquid roll moment and liquid side moment

Abstract : Spinning projectiles carrying liquid payloads and performing large coning motion have uniformly been observed to experience rapid despin. For linear fluid mechanics, it has been shown that the ratio of the magnitudes of the liquid roll moment to the liquid side moment is the tangent of the coning angle. The validity of this relationship is demonstrated by gyroscope data obtained by M. C. Miller and flight data for twelve projectiles analyzed by R. L. Pope.

Iii-Flight Measurements of the Vibration History of Spin-StabilizedProjectiles

M spin-stabilized projectiles commonly contain solid but nonrigid or liquid pay loads. These types of pay loads often produce projectile/pay load interactions that are undesirable. Vibrations of the projectile/pay load assembly could impair the performance of military fuzing, especially if that fuzing is mechanical in nature. In some instances, the timer is mechanical, but normally all fuzes have mechanical arming and safety devices. Projectile designers during test sequences often report fuze malfunctions, but little is known about the vibration environment of an artillery projectile during flight. In response to this need, an instrumentation package consisting of a strain gage bridge/attitude sensor and a telemetry unit was built and successfully tested. Several types of units were flight tested and data showing undesirable vibration histories during the flight of a projectile have been recorded.' Data from 155mm projectiles with liquid payloads are discussed. A standard yawsonde body was modified to accommodate a Wheatstone bridge. The bridge was located on a flat machined onto the cylindrical portion of the yawsonde body which extends into the ogive of a parojectile (Fig. 1). This flat was located 90 deg from the optical sensors of the yawsonde. Wires that provide voltage input and resistance measurements were located in a groove. These wires were brought through a hole in the groove to the interior of the yawsonde. The strain gages were semiconductor types and required amplification for telemetering. The output of the bridge circuit was not calibrated in such a fashion as to provide meaningful measurements of strain. Rather, the outputs of all units were adjusted for maximum sensitivity to variations in strain, i.e., vibrations. The output of the bridge circuit will be directly affected by the spin and yaw of the projectile; hence, yawsonde data are needed to interpret the vibration history of a particular projectile flight. The angular and spin motions of a projectile are traced by a yawsonde. The projectile motion is presented in terms of oN and 0 vs time. The complement of the angle between a vector drawn to the sun and a vector aligned with the spin axis of the projectile is aN, while is the derivative of the projectile's Eulerian roll angle with respect to the sun plane, i.e., the plane containing the missile's axis and the sun. The output of the strain gage bridge is an indicator of a fluctuating strain, and a spectral analysis can reveal the frequency content of these fluctuations. The presence of a particular frequency component implies that the projectile is experiencing a measurable mechanical strain at that frequency. For example, all projectiles experienced strains produced by the spin and yaw motions at the spin and yaw rates. As seen from Fig. 2, the Fourier transform of the bridge