Additional Inertial Forces Research Articles

Unsteady Flow Behaviors and Vortex Dynamic Characteristics of a Marine Centrifugal Pump under the Swing Motion

Due to the effects of swing motion, the performances and internal flow characteristics of marine centrifugal pump undergo some unsteady variations in the marine environment. The hydraulic test system with six degree of freedom parallel motion platform is established to study the pump performance characteristics at the different heel angles of steady roll position and pitch position. The pump head gradually decreases as heel angle increases. The pump head has decreased by 7% to reach the minimum at the 15° heel angle of roll position. At the same heel angle, the head at the roll position is lower than that at the pitch position under the rated flow condition. The fluid in the impeller passage is subjected to the additional inertial force of roll motion or pitch motion under unsteady swing motion, inducing some flow bias phenomena in the velocity field. The unsteady development of flow velocity induces the intense vortex motion, and the shedding and dissipation of interblade vortices are affected. The periodic flow-induced pulsation characteristics obviously appear in the impeller passage. The pulsation periodicity and pressure amplitude are influenced due to the swing motion. The pitch motion induces the greater hydraulic excitation and fluid-induced vibration amplitude. In addition to the pressure pulsation at the low frequencies, the pulsation amplitude at 20 times the shaft frequency is evident under pitch motion.

Vibration characteristics of dual-rotor system with staggered-type double elastic ring squeeze film dampers under maneuvering flight

The vibration of the rotor system is significantly intensified during maneuvering flight, rendering traditional elastic ring squeeze film dampers (ERSFDs) insufficient or unstable. To improve the applicability of dampers, a novel structure of staggered-type double elastic ring squeeze film dampers (SDERSFD) is proposed in this paper. Through the synergistic effect of double elastic rings, the damping effect is significantly enhanced, and the circumferential stiffness anisotropy of the damper is improved, which is more suitable for vibration reduction requirements under complex working conditions. Utilizing the Reynolds equation, the internal and external pressure field control equations of the double elastic rings are established. The finite difference method is then employed to solve the dynamic characteristics of the damper. Additionally, a finite element model of the dual-rotor system with SDERSFDs considering complex dynamic factors such as unbalanced force, oil film force, gravity, and additional inertial force caused by maneuvering flight is established for the study of nonlinear rotor dynamic characteristics and the analysis of SDERSFDs vibration reduction effect. Based on the model, the influence of various factors such as maneuvering speed, maneuvering radius, rotor speed and unbalance on the transient response of dive-pull up condition is analyzed. The results reveal that during dive-pull up, the vibration of the rotor system intensifies significantly. When compared with the ERSFDs, the SDERSFDs effectively reduce the vibration amplitudes of the rotor system under maneuvering flight condition, achieving the maximum vibration reduction ratio of 48.9%. Furthermore, the SDERSFD exhibits robustness against large maneuvering loads, enhancing the stability of the rotor system under extreme conditions.

Experimental and numerical investigation of the elliptical cyclone separator manufactured by 3D printing

Whether the cyclone separators have a high-efficient body shape is a problem that has been ignored for a long time. A series of cyclones with elliptical bodies were designed and manufactured by SLA 3D-printing. The separation performance and flow field of the cyclones were investigated using the experimental and CFD methods, respectively. The detailed flow features, such as streamlines, pressure and velocity profile distribution, and special flow phenomena of the circumferential acceleration/deceleration of the swirling gas, are analyzed. The experimental results reveal that the elliptical cyclones with a/b = 1.2 and 0.83 have about 2% increment of separation efficiency and 43% reduction of pressure drop, as well as satisfactory robustness to the particle properties and operating conditions. The circumferential acceleration/deceleration of the swirling gas creates an additional inertial force for the particles, thereby improving the elliptical cyclones' performance. The results provide innovation ideas for designing and manufacturing the better-performance cyclones.

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%.

Experimental study on flow rate and pressure drop characteristics in T-junction pipes under rolling conditions

Numerous T-junction circular channels are used in the pipeline system of marine dynamic platforms. Unlike terrestrial conditions, the fluid inside the channels experiences additional inertial forces due to rolling motion, leading to complex and variable fluid mixing characteristics within T-junction pipes. The flow and pressure drop characteristics were investigated inside the T-junction pipe under rolling motion conditions, including the average value, the fluctuation value, and the instantaneous value. The working fluid is considered as the de-ionized water. The inlet Reynolds number of the main pipe ranges from 2110 to 25 320, and the flow rate ratio is from 1 to 20. The rolling time and angle are 5–15 s and 0°–15°, respectively. The range of rolling Reynolds number is 0–3520. The results indicate that the influence of the rolling motion on the flow and pressure drop characteristics inside the T-junction pipe depends on the inertial force of the fluid itself. When the inertial force of the fluid itself is large, the influence of the rolling motion on the flow parameters will be weakened. The rolling motion has a greater impact on the branch than on the main pipe. Predictive relationships for flow rates and pressure loss coefficients are established under the stationary and rolling conditions, respectively, with a fitting error of less than 10%. In addition, the boundary that ignores the influence of rolling motion on flow fluctuations and the criteria for identifying fluid backflow are also proposed.

Theoretical and experimental study on the dynamic behavior of spur gear transmission system during hovering maneuver flights

Gear transmission systems, a crucial component of aircraft power transmission, are subjected to time-varying additional inertial forces and gyroscopic moments in noninertial frame environments when the aircraft performs maneuvering flight actions. In this study, a noninertial frame dynamic model of the gear transmission system during hovering maneuver flights was established, and the accuracy of the theoretical model was verified through conducting hovering maneuver flight simulation experiments. The dynamic behavior of the gear transmission system housing, bearings, and shafts under different hovering maneuver flight parameters was studied. The findings reveal that the maneuvering acceleration of the carrier causes varying degrees of change in the vibration acceleration of the housing, the center distance of the gear pair, the bearing force, and the bending deformation of the shafts, among which the magnitude and direction of the radial bearing force and shaft bending deformation are significantly affected by the maneuvering acceleration. Moreover, the risk of failure can be mitigated through the adjustment of the inclination angle to minimize the bending deformation of the fragile shaft resulting from maneuvering acceleration.

Analysis of coolant flow distribution characteristics at core inlet of small pressurized water reactor under rolling condition

The flow distribution characteristics at core inlet directly determines the thermal and hydraulic characteristics in the core, and it is closely related to the safety of nuclear reactor. The primary coolant is subjected to additional inertial force in ocean motion, which influence the flow distribution characteristics at core inlet. In the present paper, numerical simulation method is adopted to analyze the coolant flow distribution characteristics at core inlet of the Reactor Pressure Vessel (RPV) of a Small Reactor under rolling condition. Then the results of the flow distribution characteristics were compared with those under steady state. The results show the variation range of flow distribution factors in each channel under rolling condition is within 5%. And the uneven distribution of coolant at the core inlet increases with the increase of rolling amplitude, and decrease with the rolling period in short period. Standard deviation of flow distribution factor at the core inlet changes little under rolling condition, which indicates the flow distribution at the core inlet keeps good uniformity.

ФОРМИРОВАНИЕ РАСЧЕТНЫХ СХЕМ ОБОБЩЕННЫХ КИНЕМАТИЧЕСКИХ УСТРОЙСТВ, ПРИЦЕЛЬНО РЕГУЛИРУЮЩИХ СПЕКТР ЧАСТОТ СОБСТВЕННЫХ КОЛЕБАНИЙ УПРУГИХ СИСТЕМ С КОНЕЧНЫМ ЧИСЛОМ СТЕПЕНЕЙ СВОБОДЫ МАСС, У КОТОРЫХ НАПРАВЛЕНИЯ ДВИЖЕНИЯ ПАРАЛЛЕЛЬНЫ, НО НЕ ЛЕЖАТ В ОДНОЙ ПЛОСКОСТИ

To date, for some elastic systems with a finite number of degrees of mass freedom, in which the directions of mass movement are parallel and lie in the same plane, methods have been developed for creating additional generalized targeted constraints and generalized targeted kinematic devices. Each generalized targeted constraint increases, and each generalized targeted kinematic device reduces the value of only one selected natural frequency to a predetermined value, without changing the remaining natural frequencies and natural modes. Earlier, for elastic systems with a finite number of degrees of mass freedom, in which the directions of mass motion are parallel, but do not lie in the same plane (for example, plates), an approach for the computing of a matrix of additional stiffness and a method for the development of computational schemes of additional generalized targeted constraints were developed. Also earlier, for such systems, an approach was proposed for the computing of a special matrix with allowance for additional inertial forces that determine a generalized targeted kinematic device. At the same time, the method of development of computational schemes of kinematic devices was not proposed. The first part of the paper was devoted to approach, that made it possible to develop computational schemes of generalized targeted kinematic devices for such systems as well. A variant of the computational scheme of constraint for the rod system with one degree of activity was considered. Some special properties of such targeted kinematic devices were revealed. The distinctive second part of the paper is devoted to corresponding samples of analysis.

ФОРМИРОВАНИЕ РАСЧЕТНЫХ СХЕМ ОБОБЩЕННЫХ КИНЕМАТИЧЕСКИХ УСТРОЙСТВ, ПРИЦЕЛЬНО РЕГУЛИРУЮЩИХ СПЕКТР ЧАСТОТ СОБСТВЕННЫХ КОЛЕБАНИЙ УПРУГИХ СИСТЕМ С КОНЕЧНЫМ ЧИСЛОМ СТЕПЕНЕЙ СВОБОДЫ МАСС, У КОТОРЫХ НАПРАВЛЕНИЯ ДВИЖЕНИЯ ПАРАЛЛЕЛЬНЫ, НО НЕ ЛЕЖАТ В ОДНОЙ ПЛОСКОСТИ

To date, for some elastic systems with a finite number of degrees of mass freedom, in which the directions of mass movement are parallel and lie in the same plane, methods have been developed for creating additional generalized targeted constraints and generalized targeted kinematic devices. Each generalized targeted constraint increases, and each generalized targeted kinematic device reduces the value of only one selected natural frequency to a predetermined value, without changing the remaining natural frequencies and natural modes. Earlier, for elastic systems with a finite number of degrees of mass freedom, in which the directions of mass motion are parallel, but do not lie in the same plane (for example, plates), an approach for the computing of a matrix of additional stiffness and a method for the development of computational schemes of additional generalized targeted constraints were developed. Also earlier, for such systems, an approach was proposed for the computing of a special matrix with allowance for additional inertial forces that determine a generalized targeted kinematic device. At the same time, the method of development of computational schemes of kinematic devices was not proposed. The first part of the paper was devoted to approach, that made it possible to develop computational schemes of generalized targeted kinematic devices for such systems as well. A variant of the computational scheme of constraint for the rod system with one degree of activity was considered. Some special properties of such targeted kinematic devices were revealed. The distinctive second part of the paper is devoted to corresponding samples of analysis.

The effect of vibration on droplet dynamics and heat transfer of spray cooling

The heat transfer mechanism of spray cooling under vibration has yet to be revealed, so it is crucial to deeply analyze the droplet impingement dynamics and heat transfer mechanism under vibration. However, there is still a gap in analyzing how vibration quantitatively affects droplet impingement dynamics and heat transfer performance. To fill this research gap, this paper will employ high-speed cameras to quantitatively analyze droplets' dynamics and heat transfer properties under various vibrational conditions. The results demonstrate that droplet spreading is enhanced at high-frequency conditions, but the enhancement decreases with the reduction in amplitude. Under high amplitude conditions, droplets gain additional inertial forces to overcome adhesive forces, causing oscillation in the three-phase contact line of the droplets, which significantly consumes the kinetic energy of droplet spreading, thereby suppressing droplet spreading. Vibration overall suppresses droplet spreading; at an amplitude of 0.2 mm and frequency of 80 Hz, the spreading enhancement factor is merely 4 %. Moreover, the droplet's heat transfer rate, heat flux, heat transfer coefficient, and cooling efficiency all increase with the rise in vibrational frequency but are all subdued by the amplitude. Compared to a static surface, vibration suppresses droplet heat transfer but can facilitate droplet heat transfer under low amplitude and high-frequency conditions. At an amplitude of 0.2 mm, the maximum heat transfer enhancement factor (HTEF) is 16 %. At an amplitude of 0.8 mm and frequency of 10 Hz, the minimum HTEF is −44 %. This research undoubtedly brings innovative insights into spray droplet impact dynamics and heat transfer and can provide valuable guidance for related industrial applications.

DEVELOPMENT OF COMPUTATIONAL SCHEMES OF GENERALIZED KINEMATIC DEVICES THAT PRECISELY REGULATE THE NATURAL FREQUENCY SPECTRUM OF ELASTIC SYSTEMS WITH A FINITE NUMBER OF DEGREES OF MASS FREEDOM, IN WHICH THE DIRECTIONS OF MOTION ARE PARALLEL, BUT DO NOT LIE IN THE SAME PLANE

To date, for some elastic systems with a finite number of degrees of mass freedom, in which the directions of mass movement are parallel and lie in the same plane, methods have been developed for creating additional generalized targeted constraints and generalized targeted kinematic devices. Each generalized targeted constraint increases, and each generalized targeted kinematic device reduces the value of only one selected natural frequency to a predetermined value, without changing the remaining natural frequencies and natural modes. Earlier, for elastic systems with a finite number of degrees of mass freedom, in which the directions of mass motion are parallel, but do not lie in the same plane (for example, plates), an approach for the computing of a matrix of additional stiffness and a method for the development of computational schemes of additional generalized targeted constraints were developed. Also earlier, for such systems, an approach was proposed for the computing of a special matrix with allowance for additional inertial forces that determine a generalized targeted kinematic device. At the same time, the method of development of computational schemes of kinematic devices was not proposed. The distinctive paper is devoted to approach, that makes it possible to develop computational schemes of generalized targeted kinematic devices for such systems as well. A variant of the computational scheme of constraint for the rod system with one degree of activity, is considered. Some special properties of such targeted kinematic devices are revealed.

Experimental verification and performance evaluation of an inertia-type bidirectional isolation system

Both horizontal and vertical ground motion can cause damage to vibration-sensitive equipment. However, most mature seismic isolation devices only isolate horizontal ground acceleration; few devices isolate both vertical and horizontal ground acceleration. In this paper, a novel inertia-type bidirectional isolation system (IBIS) is proposed that comprises independent vertical and horizontal seismic isolators. The IBIS’s vertical isolator comprises leverage apparatus with a counterweight, which provides a vertical lifting force in the static state to balance the self-weight of the isolated object, and an additional inertial force in the dynamic state, resulting in higher static but lower dynamic effective vertical stiffness. The horizontal isolator is a conventional sliding-type system comprising a sliding platform and pair of springs. The IBIS’s equations of motion are derived by using Lagrange’s equation, and the theoretical model is verified through shaking-table test results. Numerical simulation and experimental results show that the IBIS has an anti-resonance property in the vertical direction, leading to higher isolation performance under both near-fault and far-field ground acceleration. The conventional sliding-type horizontal isolator component performs well under far-field ground acceleration but may perform unsatisfactorily under near-fault ground acceleration.

Numerical investigation on effects of rib shapes on oscillating flow and heat transfer in heat exchanger channels

Ribs are straightforward and cost-effective to improve the heat exchange efficiency, and the impact of cooling medium driven by the movement of the channel itself can also enhance the heat exchange capacity. This paper investigates the flow patterns of the gas–liquid two-phase flows in a smooth cubic and a cubic with semi-circular ribs by using a high-speed camera under different low-frequency oscillations. A numerical simulation method was used to study the impact of different ribs on each wall at various frequencies. The microscopic flow and heat transfer characteristics of the ribs were analyzed. Reflux occurred near ribs, and the fluid accumulated near the wall under the ribs with a liquid coverage ratio of approximately 79%. After the gas–liquid two-phase flow fully oscillated in the channel, the heat transfer contribution of the top wall to the entire channel reached the greatest value of approximately 40%, and the left and right walls contributed to the entire channel with 21% and 27%, respectively. An additional inertial force of the two-phase flow was sustained in the oscillating environment to form a periodic impingement flow on the rib and hence improve heat transfer. Due to the reflux near the rib, the local minimum values of the heat transfer coefficient appeared on the downwind of the rib. The difference in rib design affected the fluid motion and caused different heat transfer distributions on the top surface. These findings can support the application design of ribs in dynamic heat exchange channels for optimizing heat transfer.

Experimental investigation on the flow patterns in a T-junction under steady and rolling motion conditions using PLIF

Flow mixing experiments are performed on the Ocean Conditions Simulation Platform (OCSP) test facility to investigate the flow pattern evolution mechanisms in a T-junction with branch jet under steady and rolling motion conditions. Plane Laser-Induced Fluorescence (PLIF) technology is used to display and test the instantaneous flow pattern in the T-junction. The effects of the main fluid Reynolds number, inflow rate ratio and rolling Reynolds number on the flow pattern characteristics are discussed at a range of 2110–15850, 1–20 and 0–3520, respectively. Based on the experimental results, new classification criteria of flow pattern in the T-junction under steady condition are proposed from the perspective of the evolution of vortex structure. The flow patterns are classified into the single shear vortex, co-rotating vortex pair, transition region and counter-rotating vortex pair according to the fluid Reynolds number and inflow rate ratio. Under rolling motion condition, the branch jet periodically sweeps up and down in the T-junction due to the effect of additional inertial force. The sweeping phenomenon of the branch jet caused by rolling motion enhances the flow instability in the T-junction that can be inhibited by increasing the fluid Reynolds number or decreasing the inflow rate ratio and rolling Reynolds number. In addition, the influence mechanisms of fluid Reynolds number, inflow rate ratio and rolling Reynolds number on the flow pattern in the T-junction are investigated. These results can inform the analysis, design, safe operation and performance improvement of equipment in various industrial applications involving flow mixing in a T-junction.

Role of dynamic unbalance in dynamics of turbocharger rotors

Rotating unbalance is one of the key reasons for high vibration levels in turbochargers. The current studies consider the rotating unbalance as a series of static (force) unbalances and acknowledge the importance of their allocation and orientation. However, the displaced mass or material nonhomogeneity, which is the source of the unbalance in real-world rotors, results also in so-called dynamic unbalance. Such an unbalance creates nonzero products of inertia relative to the axis of rotation, meaning that the central principal axis does not coincide with the axis of rotation. The rotor is subjected to additional inertial forces, described in this research using a multi-body dynamics formalism. The results indicate that the dynamic unbalance amplifies the synchronous vibration and induces several types of asynchronous motions. The phenomena described in the article were proven experimentally in previous works but have been difficult or impossible to simulate without using unrealistically high values of the static unbalance. Furthermore, the work provides fundamental results regarding the interaction between the static and dynamic unbalance and proposes analytic relations describing how the balancing procedure affects the products of inertia.

Numerical study of mixed and free convection heat transfer under ocean conditions

The mixed and free convection heat transfer of vertical upward flow under ocean conditions is studied numerically. The turbulent heat transfer in a smooth circular tube at low flow rates and the effects of ocean conditions are validated by experimental data. A CFD method based on the v2-f turbulence model and additional inertial force is established. The analysis indicates that the effects of ocean conditions on heat transfer depend on the Buoyancy parameter. In particular, for the mixed convection regime, the overall heat transfer increases, and the local heat transfer deterioration is aggravated. The mixed and free convection heat transfer under ocean conditions is dominated by the Coriolis force and gravity, so the influence of rolling radius is weak. As the rolling period increases, the heat transfer variation increases due to the inclination effects. However, as the rolling amplitude increases, the heat transfer behavior is non-monotonic and difficult to predict due to the combined action of Coriolis effects and buoyancy effects. The introduction of pulsating flow breaks the symmetry of heat transfer, and the hot spot only appears on one side. The overall heat transfer increases, but the local heat transfer deterioration is further aggravated.

Numerical analysis of passive safety injection driven by natural circulation in floating nuclear power plant

The traditional energy supply paradigm has been difficult to meet the demands of ocean resources development. As a combination of small nuclear reactors and offshore platforms, the floating nuclear power plant(FNPP) can be well used in offshore energy supply. Considering passive safety injection of FNPP will be deeply affected by the ocean environment, the present study brings a CFD customization model to assess the injection process. The additional inertial force is implanted into the momentum equation to simulate motion conditions. The combination of coordinate transformation and grid traversal is used to output critical parameters. Therefore, it can be seen the overall evolution process and the local flow characteristics of natural circulation intuitively apart from quantitative analysis, making up for the deficiency of the previous analysis code. Results suggested the injection process can be divided into several stages. Affected by ocean conditions, the flow rate in FNPP will decrease with periodic fluctuation after a linear increase, so the safety injection can be completed in 180 s under static conditions while needing more than 240 s under rolling. However, although additional acceleration weakens the driving force of natural circulation, liquid sloshing and disturbed flow will make the reactor core cool more effectively.

Seismic stability of a circular tunnel in cohesive-frictional soils using a stable node-based smoothed finite element method

This paper presents the effect of horizontal and vertical earthquake force on the stability of a single circular tunnel in cohesive-frictional soils using a stable node-based smoothed finite element method (SNS-FEM). In this study, seismic forces are computed as horizontal and vertical pseudo-static body forces arising on the soil and additional inertial forces associated with the uniform surcharge applied to the ground surface. In the upper bound limit analysis based on SNS-FEM, the soil behaviour is described as rigid-perfectly plastic materials, and plasticity deformation obeys the associated flow rule following the Mohr-Coulomb failure criterion. Firstly, the numerical results were checked against other numerical solutions in the literature. The present results agree with prior contributions, proving that the proposed approach can give efficient and reliable solutions to the stability number. Secondly, the variations of the seismic stability number with changes in the horizontal earthquake acceleration coefficient were intensively investigated for different values of soil properties, internal friction angleand the depth-to-diameter ratio of the tunnel. It is shown that the seismic stability numbers of circular tunnels reduce remarkably with the increase of horizontal seismic coefficientand the soil weight. Thirdly, the seismic stability numbers were summarised in design charts for practical use in geotechnical engineering.

An analysis on a rigid-flexible coupling system of an oscillating mass and a rotating disk

A mass-rod-disk system consisting of an oscillating mass attached to a rigid rotating disk by an elastic rod is designed to study rigid-flexible coupling mechanism. Suppose the rod is lightweight and has enough stiffness, the theorems of linear momentum and angular momentum are applied to the mass-rod-disk system based on the kinematic description of the system. With respect to two deflections of the mass and one angular velocity of the system, a group of nonlinear differential equations are established where the tangential inertial force, centrifugal force, Coriolis force as well as the moments of additional inertial forces take important effects on the dynamic response. For the sake of description, these three types of inertial forces mentioned before are referred to as additional inertial forces in this paper. The horizontal deflections of the mass and the angular velocity of the disk rotating about a fixed-axis are numerically solved for the prescribed external torque. The oscillating trajectory of the mass is deeply influenced by the additional inertial forces, meanwhile the dynamic fluctuations of the angular velocity and rotary inertia of the system are strongly affected by the mass oscillation.

Experimental study of pool boiling heat transfer under rolling condition

Many heat exchangers inside ocean nuclear power plants (ONPPs) adopt pool boiling, and the additional inertial forces derived from complicated ocean motion will induce some unique thermohydraulic characteristics, which are still remaining to be further elucidated. In this paper, effects of rolling condition on pool boiling heat transfer are experimentally investigated by using the six-freedom platform. The variation of inertial forces during rolling periods are analyzed, and observations of bubble unique behaviors about nucleation, growth, coalescence, departure and wagging under rolling condition are implemented to verify the rolling effects on pool boiling heat transfer. The results show that rolling motion enhances pool boiling in both regions of natural convection and nucleate boiling. Maximum 23.9 % higher heat transfer coefficient (HTC) and 8.1 % higher critical heat flux (CHF) are obtained under rolling condition with amplitude A = 26° and period tp = 5 s. Bubble nucleation is improved by the rolling motion, which decreases the superheat degree at onset of nucleate boiling (ONB) and increases the nucleation site four times at this moment. Small bubbles grow and coalesce more drastically under rolling condition, and bubble departure is accelerated, with 11 %–19 % reduction of departure diameter and 23 %–32 % increase of departure frequency. This work can not only present fundamental mechanism for pool boiling heat transfer under rolling condition, but also serve as useful guidelines for designing pool boiling heat exchangers inside ONPPs.