Effect Of Rolling Motion Research Articles

Numerical investigation on the effects of heel on the aerodynamic performance of wing sails

The utilization of wind-assisted propulsion technology could reduce ship fuel consumption and emission of pollutants. In the study, the effect of steady heel angles on the aerodynamic characteristics of wing sails was investigated. Full-scale three-dimensional simulations with the ship's superstructure were conducted at heel angles of 0°–15° in all apparent wind directions. The correctness of the numerical computations is verified by comparing them with the wind tunnel experimental data. Overall, the heel is detrimental to the capture of wind energy by the wing sails. The aerodynamic forces of the sail system decrease with increasing heel angles. Specifically, the average thrust performance is attenuated by 4.7%, 13.5% and 20.5%, respectively, at heel angles of 5°, 10°, and 15° compared to the upright condition. Due to changes in the airflow distribution around the sails, the aerodynamic force of sails in heeled to windward and heeled to leeward decreases by the reduced area of the low-pressure zone on the suction side and the high-pressure zone on the pressure side, respectively. Finally, a prediction scheme for assessing the effect of rolling motion on sail performance is proposed by steady heel results.

Theoretical study on pressure oscillation dominant frequency of bubbles submerged jet under rolling condition

Steam direct contact condensation is a highly efficient heat and mass transfer phenomenon, usually accompanied by strong mass, momentum and energy exchanges at the water-steam interface, which can rapidly realize cooling and pressure relief, but also accompanied by pressure oscillations. When the relevant equipment is used in offshore nuclear power plants and naval non-energetic systems, the additional inertial force field caused by ocean motion may cause greater harm to the safe operation of the relevant devices. Therefore, a theoretical study is conducted to investigate the effect of rolling motion on dominant frequency of steam submerged jets pressure oscillation with low mass fluxes. Firstly, based on bubble dynamics theory, a theoretical model of bubble condensation oscillations under rolling motion with low mass flux is established. Then, the mechanism of the rolling conditions on the dominant frequency of pressure oscillation is analyzed from the aspect of theoretical derivation. Finally, on the basis of the potential flow function theory and small perturbation theory, the predicted correlation of pressure oscillation dominant frequency under the rolling motion with low mass flux is derived, and compared with the numerical simulation results, the prediction deviation is within ±10%.

Study on multi-scale coupled simulation of natural circulation system with 3×3 petal-shaped fuel bundle channel under rolling condition

Petal-shaped fuel rod encompasses a broad application prospect in sea-based nuclear power plants. A multi-scale coupled simulation is conducted based on natural circulation system with 3×3 petal-shaped fuel bundle channel. A multi-scale coupled model considering rolling motion is developed. Its reliability is verified by existing experimental data. The effect of rolling motion on the characteristics of natural circulation system is thoroughly discussed. The results indicate that if the start-up direction of rolling motion is the same as the direction of flow rate, rolling motion will lead to a sharp decrease in flow rate at the initial moment. By increasing rolling amplitude or decreasing rolling period will cause a significant increase in fluctuation amplitude of flow rate. Compared with the results under static condition, the fluid is subjected to the Coriolis force in the non-inertial coordinate system. This research can provide support for the joint optimization of natural circulation system.

Pressure fluctuations preceding critical heat flux during subcooled flow boiling in a one-side heated mini-channel under rolling motion

This study investigates effects of rolling motion on pressure fluctuations leading to Critical Heat Flux (CHF) during subcooled flow boiling in a mini-channel. Experiments were conducted at rolling amplitudes of 15° and 25° and periods of 10 and 30 s under two mass flow rates. Results obtained in static and rolling cases were compared. The rolling case showed higher pressure fluctuations, leading to higher CHF values, compared to the static case. The rolling intensity was the highest in the case with a higher amplitude and a shorter rolling period, whereas it was the lowest in the case with a lower amplitude and a longer rolling period. Correspondingly, the pressure fluctuations and CHF followed a similar trend, with the highest values observed in the case with the highest rolling intensity. The pressure fluctuations in the rolling experiments were also found to increase with increasing power, particularly at high heat flux values.

Effects of roll motion on linear and nonlinear gap resonances in a moonpool excited by various incident-wave heights

The linear and nonlinear gap resonances in a free-rolling moonpool are investigated using a two-dimensional in-house code based on the constrained interpolation profile method. This study primarily focuses on the effects of roll motion on hydrodynamic characteristics, taking into account both the linear gap resonance and the nonlinear process-driven gap resonances. The analysis of the incident-wave height is conducted to illustrate the relationship between higher-order harmonics and nonlinear gap resonances. Numerical results demonstrate that the resonant frequency is insensitive to the roll motion. However, the roll response plays an important role in influencing the vertical wave loads on the barges and affecting the energy conversion pattern in the fluid field. According to the analysis of the incident-wave height parameter, the magnitudes of resonance at the linear and nonlinear resonant points are approximately in sub-linear and superlinear relationships with the incident-wave height, respectively. Moreover, the vortex shedding modes around the entrance of the free-rolling moonpool gradually transit from being dominated by the pairs of vortices to being dominated by the single vortex as the gap resonance changes from linear to quartic.

Hydrodynamics and Wake Flow Analysis of a Floating Twin-Rotor Horizontal Axis Tidal Current Turbine in Roll Motion

The study of hydrodynamic characteristics of floating double-rotor horizontal axis tidal current turbines (FDHATTs) is of great significance for the development of tidal current energy. In this paper, the effect of roll motion on a FDHATT is investigated using the Computational Fluid Dynamics (CFD) method. The analysis was conducted in the CFD software STAR-CCM+ using the Reynolds-averaged Navier–Stokes method. The effects of different roll periods and tip speed ratios on the power coefficient and thrust coefficient of FDHATT were studied, and then the changes in the vorticity field and velocity field of the turbine wake were analyzed by two-dimensional cross-section and Q criterion. The study indicates that roll motion results in a maximum decrease of 30.76% in the average power coefficient and introduces fluctuations in the instantaneous load. Furthermore, roll motion significantly accelerates the recovery of wake velocity. Different combinations of roll periods and tip speed ratios lead to varying degrees of wake velocity recovery. In the optimal combination, at a position 12 times the rotor diameter downstream, roll motion can recover the wake velocity to 92% of the incoming flow velocity. This represents a 23% improvement compared to the case with no roll motion.

Effects of rolling motion on helical coil once-through steam generator thermal-hydraulic characteristics

Steam generators are essential for the safe, economical, and reliable operation of nuclear reactors. Helical Coil Once-through Steam Generators (HCOTSG) offer unique advantages over other types of steam generators for ship reactors or offshore platforms. To investigate the effect of rolling motion due to ocean conditions on the safe and economic operation of HCOTSG, a new model and a new code are developed in this paper. The program is developed and allows numerical simulation of HCOTSG under ocean conditions. The validity of the code was verified by comparing the simulation results with the design parameters of the Marine Reactor X (MRX) steam generator and the simulation results of other dedicated programs. The code was further used to perform the International Reactor Innovative and Secure (IRIS) transient operating conditions under typical rolling motions. Then, the influences of different swing directions, angles, periods, and positions of swing axes from the origin of the system operating parameters are analyzed.In the cases discussed in this paper, the following conclusions are obtained: (a) The direction of the swing significantly affects the system. The most dangerous situation is around the x-axis, and the case around the z-axis is the safest, in which the rolling situation has little effect on the system because the centripetal force is perpendicular to the tube wall, and the gravitational pressure drop is constant. (b) when the swing angle increases, except the fluctuation speed is faster, the fluctuation range of the parameters also increases. (c) when the swing period changes, the parameters’ fluctuation range also change (d) the orientation of the swing axis from the origin affects the magnitudes of the parameters’ changes (e) the distance of the swing axis from the origin affects the magnitude of the parameter variation and the farther the swing axis is from the origin, the greater the parameter fluctuation.

Research on effects of rolling motion on a pressurizer surge line based on the fluid-solid-thermal coupling method

To investigate the effects of rolling motion on the thermal stress and deformation caused by thermal stratification of a pressurizer surge line in floating nuclear power plants (FNPP), the finite element simulation platform ANSYS Workbench 19.0 is utilized to conduct the fluid–solid-thermal coupling transient analysis of the surge line under different rolling motion conditions. The Large Eddy Simulation (LES) approach and the Frame Motion model are used in Computational Fluid Dynamics (CFD) analysis. By comparing different calculated results, it is found that rolling motion can significantly improve thermal stratification and reduce the peak thermal stress in some positions of the surge line, but may also result in periodic oscillations in temperature and thermal stress. The effects of the rolling period and the maximum rolling angle on the oscillation amplitude of temperature and thermal stress are investigated. This work provides a reference for evaluating pipeline fatigue damage and the structural integrity of the pressurizer surge line in FNPP under actual ocean conditions.

Experimental study on condensation heat transfer characteristics in C-shaped tube under rolling conditions

C-shaped tube heat exchanger has the advantages of good performance in heat transfer, space-saving, and reliability, and thus it has great potential to be used as passive residual heat removal heat exchanger in offshore nuclear power plants. In the present study, the condensation heat transfer characteristics in a C-shaped tube, which is the basic unit of C-shaped tube heat exchanger, were investigated experimentally, and the experiment was carried out under steady state and rolling conditions respectively. The effect of heat flux and rolling conditions on the condensation heat transfer characteristics were studied. The heat flux varies from 73.3 kW/m2 to 446.7 kW/m2; the rolling amplitude varies from 5° to 15°; and the rolling period ranges from 5 s to 20 s. The experimental results show that the condensation in the C-shaped tube is gravity-dominated. Based on the experiment data, a new correlation used to calculate the heat transfer coefficient of a C-shaped tube under steady state has been obtained. The rolling motion has significant effect on the condensation heat transfer of the C-shaped tube. With the increase of rolling angle from 0° to 15°, the condensation heat transfer performance of the C-shaped tube gradually increases and the increase rate of the condensation heat transfer coefficient is up to 18%. On the other hand, with the increase of rolling period from 5 s to 20 s, the condensation heat transfer performance of the C-shaped tube decreases. Further investigation revealed that, as the heat flux increases, the effect of rolling motion on the condensation heat transfer decreases.

Study on flow and heat transfer characteristics of supercritical CO2 inside horizontal tube under ocean rolling condition

The flow and heat transfer characteristics of supercritical CO2 in a horizontal tube are studied numerically under the condition of ocean rolling. It is found that the rolling motion is beneficial to alleviate the deterioration of heat transfer at the top of the tube. However, the heat transfer deterioration is performed periodically with the rolling motion, which can cause periodic fluctuations in temperature and thermal stress of tube wall. This will affect the service-life. At a relatively small mass flow rate or large heat flux, the effect of rolling motion on the heat transfer performance increases since the density difference and buoyancy is relatively large. With the increase of inlet temperature and the decrease of buoyancy effect, the influence of rocking motion on heat transfer gradually decreases. The influence of rolling motion on the heat transfer for the floating nuclear power plant should be taken into consideration in the design.

Influence of marine conditions on thermal efficiency of SCO2 Brayton cycle for waste heat recovery

The supercritical CO2 Brayton cycle has great advantages for waste heat recovery in ships. The rolling motion would affect heat transfer as well as the efficiency of Brayton cycle, but few literature have studied the influence on the cycling efficiency. In view of this, the purpose of this paper is to obtain the effect of rolling motion the Brayton cycle and clarify its mechanism. Therefore, the heat transfer characteristics as well as thermal efficiency under rolling motion are calculated by numerical simulation coupled with the inertia force. The results show that rolling conditions lead to the instability of thermal performance in the heat exchanger and likewise the instability of thermal efficiency. Specially, as the rolling cycle decreases or the angle increases, fluctuations of outlet temperature and mass flux of supercritical CO2 are enhanced, which deteriorates the instability of thermal efficiency. The main reason for the instability is the influence of additional forces on the fluid under the rolling motion. In the axial view, the rolling motion has the strong influence on the fluid in the middle section of the heat exchanger, and has the significant effect on the fluid near the wall in the radial direction.

Effect of rolling motion on transient characteristics of condensation induced water hammer in an equal-height-difference passive heat removal system

The investigation of condensation-induced water hammer (CIWH) under ocean conditions is crucial to the system safety of the offshore floating nuclear plants (OFNPs). This paper establishes a CIWH numerical model under rolling conditions based on the computational fluid dynamics (CFD) code combined with user-defined functions (UDF). First, the numerical model is verified by published experimental data. Then, the transient behaviors of CIWH events under various rolling parameters are numerically investigated. The results show that the rolling motion causes a significant steam slug and enhances the steam-subcooled water contact area, which promotes the average condensation rate. The average condensation rate increases with an increase in rolling angle, decreases with an increase in rolling period. Due to the larger average condensation rate and reverse flow caused by rolling motion, the pressure peak generated by the CIWH significantly increases compared to static conditions. Similarly, the pressure peak increases as rolling angle increases, decreases as rolling period increase. Moreover, the pressure peak is proportional to steam inlet velocity, and the location of the pressure peak gradually moves back to the outlet direction as the steam velocity increases. These qualitative conclusions are useful to understand the effects of rolling motion on the CIWH and provide a reference for the CIWH simulations.

Application of particle image velocimetry on velocity distribution in 5 × 5 rod bundle channel under rolling motion

The Floating Nuclear Power Plant (FNPP) would be in rolling motion during operation. The rolling motion will introduce fluctuated inertial force periodically, resulting in periodic thermal and hydraulic parameters variation, and may threaten the reactor's safety. An experimental investigation was conducted to study the influence of rolling motion on flow characteristics to measure the flow field in 5 × 5 rod bundles by Particle Image Velocimetry (PIV) under rolling motion. Results show that the rolling motion can cause a strong secondary flow. The rolling motion has little effect on the central sub-channels but significantly influences the external sub-channels. When the Reynolds number is low, the external sub-channels will periodically backflow. This study shows that the flow field affected by rolling motion differs from the pulsating flow. The applicability of using pulsating flow to study the effects of rolling motion needs further evaluation, and the results can provide a reference for numerical simulations.

Effects of rolling motion on flow and heat transfer characteristics in a tube bundle channel

The usage of nuclear energy in the ocean is growing, and the most significant fundamental motion of ocean conditions is rolling motion. Due to the significant quantity of tube bundle channels in marine nuclear power equipment, it is crucial to investigate the single-phase and boiling heat transfer characteristics in tube bundle channels under rolling motion. The paper compares the single-phase convection, sub-cooled boiling, and saturated boiling heat transfer characteristics under rolling and vertical conditions. The result demonstrates that the two-phase time-averaged heat transfer is lower under rolling motion compared with that under vertical conditions, and the rolling motion has the strongest impact on the time-averaged sub-cooled boiling. Time-averaged heat transfer coefficient decreases with the increase of the rolling amplitude and period. Due to the dearth and the necessity of research on transient sub-cooled boiling under rolling motion, the instantaneous sub-cooled boiling heat transfer fluctuation characteristics are investigated. The fluctuation amplitude of the heat transfer coefficient increases with increasing rolling period and frequency. The change of bubble behavior caused by rolling motion is the main reason for the change of transient heat transfer characteristics compared with that under vertical conditions. At last, a series of correlations based on the Gungor-Winterton correlation is improved and proposed to predict the instantaneous sub-cooled boiling heat transfer coefficient. Thereinto, the average relative error is 7.36% for forecasting the time-averaged heat transfer coefficient, and the average relative error for predicting the fluctuation amplitude of the heat transfer coefficient is 11.58%.

Numerical simulation of flow resistance characteristics in a rod bundle channel under rolling conditions

Flow resistance characteristics in a 3 × 3 rod bundle channel under rolling motion are investigated by numerical simulation to overcome the limitation of experimental conditions and measurement methods. Severe rolling conditions are selected to make up for the lack of test range. The local parameters, including flow field, temperature field and wall shear stress are given to analyze the influence mechanism of the rolling motion on friction resistance of the rod bundle channel. Under rolling conditions, the absolute value of flow rate does not influence the fluctuation amplitude of frictional pressure drop when inlet flow rate does not fluctuate. Additional pressure drop is the main factor affecting the fluctuation amplitude of frictional pressure drop under rolling conditions. When the rolling motion becomes severe, the velocity deviation increases, while it has no obvious influence on velocity peak value within cross section. Increasing the flow rate weakens the effect of rolling motion on axial velocity distribution. The variation of flow rate does not affect the magnitude and distribution of radial velocity, and the radial secondary flow intensity is mainly determined by the intensity of rolling motion. Different from velocity distribution, the wall shear stress distribution is obviously affected by rolling motion and is unconnected with flow rate, while the flow rate affects the relative value of wall shear stress. Under the same rolling parameters, the variation range of boundary layer thickness increases with decreasing flow rate, which leads to an increase in the relative variation range of wall shear stress with decreasing flow rate.

Flow fluctuations and flow friction characteristics of lead-bismuth eutectic in a vertical tube under rolling conditions

The effects of rolling motion on the flow characteristics of lead-bismuth eutectic in a vertical circular tube are investigated experimentally. The results show that the pressure drop and flow rate of the forced LBE circulation fluctuate under rolling conditions. The effect of rolling motion on the flow characteristics decreases with the increase of the corresponding static Reynolds number. The rolling motion may increase the time-averaged frictional resistance coefficient of the LBE when flow rate is low. The critical value of the impact Reynolds number is about 125,000. As a result, the time-averaged flow rate decreases. The analysis shows that it is mainly the transverse additional force caused by the rolling motion increases the frictional resistance of the LBE. An empirical correlation is established to predict the frictional resistance coefficient under rolling conditions. This study may be useful in the design and safety analysis of LBE as a working fluid under moving conditions.

Numerical investigation of heat transfer performance and bubble behavior of nucleate pool boiling in a confined space under rolling conditions

Nucleate pool boiling process is widely used in heat exchangers because of its excellent heat transfer performance. With the gradual increase of applications, more and more equipments work in a non-static state, but there is little research under rolling conditions. Therefore, it is necessary to investigate the influence of rolling motion on the nucleate pool boiling process. In this study, a numerical investigation of the nucleate pool boiling process under static and rolling conditions is performed based on the volume-of-fluid (VOF) method. Physical fields and phase distribution under static state and rolling motion are compared to investigate the effect of rolling motion on the nucleate pool boiling process. The results show that rolling motion greatly influences the bubble behavior and void fraction owing to the differences between flow fields. The void fraction decreased by 11.84%, 48.82%, and 56.87% as the maximum rolling angle increased from 15° to 45°, and by 11.84%, 22.27%, and 21.81% as the rolling period increased from 1 s to 3 s. The void fraction decreased by 11.84%, 48.82%, and 56.87% as the maximum rolling angle increased from 15° to 45°. The heat transfer coefficients of different cases are compared, and it is found that the effects of rolling motion on heat transfer coefficients can be ignored.

Effects of rolling motion on transient flow behaviors of gas-liquid two-phase flow in horizontal pipes

The investigation of transient flow behaviors of gas-liquid two-phase flow under ocean conditions is vital to the application of gas-liquid transport in ocean engineering area. In this paper, the gas-liquid two-phase flow numerical model of rolling horizontal pipe is established based on CFD code combined with user-defined functions (UDF). The three-dimensional rolling flow fields are simulated using the volume of fluid (VOF) model, RNG k−ε turbulence model and additional inertia force method. First, the simulation results are compared with the experimental data, which revealed a reasonable agreement. Then, the variation in transient flow behaviors by horizontal pipe (L = 2.0 m, D = 0.035 m) with varying rolling conditions (θm = 2°-6°, T = 0.5–4.0 s) and flow velocities (jG = 0.1–10.0 m/s, jL = 0.1–0.5 m/s) are investigated. The results showed that the rolling motion caused agglomeration of dispersed bubbles and gas slugs into a continuous gas column, increased the cross-sectional void fraction significantly. The variation of additional inertial force and pressure drop increased with the increase of rolling angle and the decrease of the rolling period. Compared with the rolling angle, the transient flow behaviors are more sensitive to the rolling period. In addition, as the initial gas volume fraction increased, the effects of rolling motion on the transient flow behaviors decreased gradually. These qualitative conclusions may serve as a reference for gas-liquid transport simulations under rolling conditions.

Change in Turning Ability According to the Side Fin Angle of a Ship Based on a Mathematical Model

In general, the effect of roll motion is not considered in the study on maneuverability in calm water. However, for high-speed twin-screw ships such as the DTMB 5415, the coupling effects of roll and other motions should be considered. Therefore, in this study, the estimation of maneuverability using a 4-degree-of-freedom (DOF; surge, sway, roll, yaw) maneuvering mathematical group (MMG) model was conducted for the DTMB 5415, to improve the estimation accuracy of its maneuverability. Furthermore, a study on the change in turning performance according to the fin angle was conducted. To accurately calculate the lift and drag forces generated by the fins, it is necessary to consider the three-dimensional shape of the wing, submerged depth, and effect of interference with the hull. First, a maneuvering simulation model was developed based on the 4-DOF MMG mathematical model, and the lift force and moment generated by the side fins were considered as external force terms. By employing the CFD model, the lift and drag forces generated from the side fins during ship operation were calculated, and the results were adopted as the external force terms of the 4-DOF MMG mathematical model. A 35° turning simulation was conducted by altering the ship’s speed and the angle of the side fins. Accordingly, it was confirmed that the MMG simulation model constructed with the lift force of the fins calculated through CFD can sufficiently estimate maneuverability. It was confirmed that the heel angle changes according to the fin angle during steady turning, and the turning performance changes accordingly. In addition, it was verified that the turning performance could be improved by increasing the heel angle in the outward turning direction using the side fin, and that the sway speed of the ship during turning can affect the turning performance. Hence, it is considered necessary to study the effect of the sway speed on the turning performance of a ship during turning.

Effect of rolling motion with large radius on flow and heat transfer characteristics of supercritical methane in a mini channel

• Rolling results in the violent fluctuation of flow and heat transfer in supercritical methane. • Additional force along the flow direction is the key to affect the flow and heat transfer. • Hysteresis exists in the coupling of rolling, flow fluctuation and temperature fluctuation. • Rolling produces greater fluctuation in the near-wall area than that in the inner center area. The offshore floating storage and regasification unit (FSRU) is developing rapidly as a new type of storage and gasification system for liquefied natural gas (LNG), and the heat transfer and system stability of offshore LNG vaporizers are greatly affected by ocean rolling. To reveal the regular pattern and mechanism of supercritical methane heat transfer performance under ocean motion, this research numerically studied the flow and heat transfer characteristics of supercritical methane in a 1 × 1 × 100 mm mini channel under the additional inertial force by large radius rolling. Based on the non-inertial coordinate system, the normal inertial acceleration, radial inertial acceleration and Coriolis inertial acceleration were considered. Moreover, Nusselt number, degree of fluctuation and friction factor were investigated. The ranges of Reynolds number and Nusselt numbers are 15,000 to 45,000 and 35 to 130 respectively. The results show that the Nusselt number and friction factor violently fluctuate under rolling motion, and the fluctuation period is similar to the rolling period. Besides, the fluctuation degree of Nusselt number is greater than that of friction factor, and the largest fluctuation degree of Nusselt number is 27.9%. The effect of the fluctuation increases with the decrease of the rolling period and the increase of the rolling amplitude. Hysteresis exists in the coupling of rolling, flow fluctuation and temperature fluctuation. In addition, the degree of fluctuation is reduced with the increase of fluid temperature and mass flux. For the effect of rolling, the additional force in the mainstream direction plays a leading role. Besides, the influence of radial force is greater than that of normal force for horizontal flow condition.