Dr Zixiang Sun

A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aerothermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead center (BDC) and the top dead center (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual gray body assumptions and Lambert's law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup.

A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aero-thermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead centre (BDC) and the top dead centre (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual grey body assumptions and Lambert's law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup. NOMENCLATURE í µí°áreaµí°área [m 2 ] Aref reference area = 0.25í µí¼‹(í µí°· í µí±œ 2 − í µí°· í µí±– 2) [m 2 ] í µí° ¶ í µí±–,í µí±— the radiosity matrix in equation 9 í µí° ¶ í µí± specific heat at constant pressure [J⋅kg-1 ⋅K-1 ] D diameter [m] Dr diameter ratio between the inner and outer cylinders =í µí°· í µí±œ í µí°· í µí±– ⁄ í µí°¹ í µí±–,í µí±— the view factor in equation 9 for radiation g acceleration due to gravity [m⋅s-2 ] H radial depth of the annular test section =(Do-Di)/2 [m] L length [m] í µí±ṧ mass flow rate [kg⋅s-1 ] í µí±š í µí±¥ ̇ mass flow rate in the positive x-direction = 0.5 ∬ í µí¼Œ(í µí±‰ í µí±¥ + |í µí±‰ í µí±¥ |)í µí±‘í µí°´í µí°´í µí°´í µí±¥ [kg⋅s-1 ] m* normalised mass flow rate = í µí±š/í µí±š í µí±Ÿí µí±’í µí±“ NuDi Nusselt number = í µí±ží µí°· í µí±– /(í µí¼…(í µí±‡ í µí±– − í µí±‡ ∞)) Pr Prandtl number = í µí° ¶ í µí± µ/í µí¼… í µí±ž heat flux [W⋅m −2 ] qconv convection heat flux [W⋅m −2 ] qrad radiation heat flux [W⋅m −2 ] qtot total heat flux = í µí±ž í µí±í µí±œí µí±›í µí±£ + í µí±ž í µí±Ÿí µí±Ží µí±‘ [W⋅m −2 ] í µí±„ heat flux integral = ∬ í µí±ží µí±‘í µí°´í µí°´í µí°´í µí±¤ [W] Q* normalised heat flux integral = í µí±„/í µí±„ í µí±Ÿí µí±’í µí±“ í µí±…í µí±Ž í µí°·í µí±– Rayleigh number = í µí¼Œí µí±”í µí»½(í µí±‡ í µí±– − í µí±‡ í µí±œ)í µí°· í µí±– 3 í µí¼‡í µí»¼ ⁄ Re í µí°·í µí±– Reynolds number = í µí¼Œí µí±ˆí µí°· í µí±– /í µí¼‡ í µí±Ÿ * normalised radial coordinate =(í µí±Ÿ − í µí±Ÿ í µí±–) í µí°» ⁄ í µí±‡ temperature [K] í µí±‡ ∞ ambient temperature surrounding the test rig í µí±‡ * normalised temperature =(í µí±‡ − í µí±‡ ∞) (í µí±‡ í µí±– − í µí±‡ ∞) ⁄ t time [s] í µí±¡ 0 shutdown cooling start time [s] í µí±¡ í µí±“ reference flow time =í µí°· í µí±– í µí±ˆ ⁄ [s] í µí±¡ * normalised flow time =í µí±¡ í µí±¡ í µí±“ ⁄ í µí±ˆ reference velocity = √í µí±”í µí»½(í µí±‡ í µí±– − í µí±‡ í µí±œ)í µí°· í µí±– [m⋅s-1 ] í µí±¢ í µí¼ shear or friction velocity = √í µí¼ í µí±¤ /í µí¼Œ [m⋅s-1 ] 2 Copyright © 2024 Rolls-Royce plc. v instantaneous velocity [m⋅s-1 ] í µí±‰ time mean velocity [m⋅s-1 ] í µí±‰ * normalised velocity =í µí±‰ í µí±ˆ ⁄ í µí±¥, í µí±Ÿ, í µí¼ƒ axial, radial and angular coordinates [m,m,º] í µí±¥, í µí±¦, í µí± § Cartesian coordinates [m,m,m] í µí±¥ * normalised axial distance =í µí±¥ í µí°» ⁄ yp wall distance [m] yp + normalised wall distance =ρypuτ/μ Greek í µí»¼ thermal diffusivity = í µí¼…/í µí¼Œí µí° ¶ í µí± [í µí±š 2 ⋅s-1 ] í µí»½ thermal expansion coefficient = 1/í µí±‡ í µí±Ÿí µí±’í µí±“ [K-1 ] í µí»¾ specific heat capacity ratio = í µí° ¶ í µí± /í µí° ¶ í µí±£ Δí µí±‡ temperature difference between the inner and outer cylinders = í µí±‡ í µí±– − í µí±‡ í µí±œ [K] Δ(í µí±¥, í µí±Ÿ, í µí¼ƒ) mesh spacing in axial, radial & angular directions í µí»¿ í µí±–,í µí±— the Kronecker delta ε emissivity for radiation í µí¼ƒ circumferential angle =atan(z/y) [°] í µí¼… thermal conductivity [W⋅í µí±š −1 ⋅K-1 ] í µí¼‡ dynamic viscosity [kg⋅m-1 ⋅s-1 ] í µí¼Œ density [kg⋅m-3 ] í µí¼Œ ∞ ambient density [kg⋅m-3 ] í µí¼Ž the Stefan-Boltzmann constant = 0.56687x10-7 [w⋅m −2 ⋅K −4 ] í µí¼ í µí±¤ wall shear stress [N⋅í µí±š −2 ] Superscript * normalised parameter Subscript av average cone cone i inner cylinder o outer cylinder ref reference parameter í µí±¥, í µí±¦ axial and vertical directions, respectively w wall Acronyms BDC bottom dead centre, θ=180º CFD computational fluid dynamics CHT conjugate heat transfer FEA finite element analysis HP high power condition LES large-eddy simulation URANS unsteady Reynolds-averaged Navier-Stokes simulation TDC top dead centre, θ=0º

Code_Saturne, an open-source computational fluid dynamics (CFD) code, has been applied to a range of problems related to turbomachinery internal air systems. These include a closed rotor-stator disc cavity, a co-rotating disc cavity with radial outflow and a co-rotating disc cavity with axial throughflow. Unsteady Reynolds-averaged Navier–Stokes (RANS) simulations and large eddy simulations (LES) are compared with experimental data and previous direct numerical simulation and LES results. The results demonstrate Code_Saturne's capabilities for predicting flow and heat transfer inside rotating disc cavities. The Boussinesq approximation was implemented for modelling centrifugally buoyant flow and heat transfer in the rotating cavity with axial throughflow. This is validated using recent experimental data and CFD results. Good agreement is found between LES and RANS modelling in some cases, but for the axial throughflow cases, advantages of LES compared to URANS are significant for a high Reynolds number condition. The wall-modelled large eddy simulation (WMLES) method is recommended for balancing computational accuracy and cost in engineering applications.

Code_Saturne, an open-source computational fluid dynamics (CFD) code, has been applied to a range of problems related to turbomachinery internal air systems. These include a closed rotor-stator disc cavity, a co-rotating disc cavity with radial outflow and a co-rotating disc cavity with axial throughflow. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations and large eddy simulations (LES) are compared with experimental data and previous direct numerical simulation (DNS) and LES results. The results demonstrate Code_Saturne's capabilities for predicting flow and heat transfer inside rotating disc cavities. The Boussinesq approximation was implemented into the code for modelling centrifugally buoyant flow and heat transfer in the rotating cavity with axial throughflow. This is validated using recent experimental data and CFD results. Good agreement is found between LES and RANS modelling in some cases, but for the axial throughflow cases, advantages of LES compared to URANS are significant for a high Reynolds number condition. The wall-modelled large eddy simulation (WMLES) method is recommended for balancing computational accuracy and cost in engineering applications.

Flow and heat transfer in an aero-engine compressor disk cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES), and coupled fluid/ solid modeling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2 deg axisymmetric and a 22.5 deg discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modeling using the axisymmetric sector model and the Spalart-Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that using a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor disks and that this could be applied in management of compressor blade clearance.

Thermal analysis of a turbine disc through a transient test cycle is demonstrated using 3D computational fluid dynamics (CFD) modeling for the cooling flow and 3D finite element analysis (FEA) for the disc. The test case is a 3D angular sector of the high pressure (HP) turbine assembly of a civil jet engine and includes details of the coolant flow around the blade roots. Proprietary FEA and CFD solvers are used to simulate the metal and fluid domains, respectively. Coupling is achieved through an iterative loop with smooth exchange of information between the FEA and CFD simulations at each time step, ensuring consistency of temperature and heat flux on the coupled interfaces between the metal and fluid domains. The coupled simulation can be completed within a few weeks using a PC cluster with multiple parallel CFD executions. The FEA/CFD coupled result agrees well with corresponding rig test data and the baseline 3D and 2D FEA solutions, which have been calibrated using test data. Provision of upstream boundary conditions and modeling of rapid transients are identified as areas of uncertainty. Averaging of CFD solutions and relaxation is used to overcome difficulties caused by CFD oscillations associated with flow unsteadiness. The present work supports the continued use and development of the FEA/CFD coupling method for industrial applications. Copyright © 2012 by ASME.

To achieve enhanced cooling of hot components in the high pressure (HP) section of an aeroengine, application of cooled cooling air (CCA) has been proposed. Here a “two row preswirl feed” arrangement is considered to accommodate the CCA, together with the uncooled cooling air (UCA) in high pressure turbine (HPT) preswirl cavity. The CCA and UCA inflows are introduced into the preswirl cavity at two different radii. Most of the cooling air leaves the preswirl cavity from the receiver holes. To assess the CCA behavior in the preswirl cavity, a definition of feeding effectiveness is introduced based on the relative total temperature at the exit of the receiver hole. The CFD investigation for the preswirl cavity was conducted in a systematic way by altering both the radial position of the receiver hole and inflows of the CCA and UCA, while keeping other conditions unchanged. It was found that the feeding effectiveness increases as the radial position of the receiver hole decreases. An optimal feeding effectiveness close to a minimum mixing condition was achieved by adjusting the CCA and UCA inflows. Unsteady CFD investigations gave a similar prediction for the overall performance of the CCA in the preswirl cavity, but with a lower feeding effectiveness compared with its steady CFD counterpart. The reduction in the feeding effectiveness was attributed to an enhanced mixing from the discrete CCA and UCA inflows and associated unsteady effects.

Use of computational fluid dynamics (CFD) to model the complex, 3D disk cavity flow and heat transfer in conjunction with an industrial finite element analysis (FEA) of turbine disk thermomechanical response during a full transient cycle is demonstrated. The FEA and CFD solutions were coupled using a previously proposed efficient coupling procedure. This iterates between FEA and CFD calculations at each time step of the transient solution to ensure consistency of temperature and heat flux on the appropriate component surfaces. The FEA model is a 2D representation of high pressure and intermediate pressure (IP) turbine disks with surrounding structures. The front IP disk cavity flow is calculated using 45 deg sector CFD models with up to 2.8 million mesh cells. Three CFD models were initially defined for idle, maximum take-off, and cruise conditions, and these are updated by the automatic coupling procedure through the 13,000 s full transient cycle from stand-still to idle, maximum take-off, and cruise conditions. The obtained disk temperatures and displacements are compared with an earlier standalone FEA model that used established methods for convective heat transfer modeling. It was demonstrated that the coupling could be completed using a computer cluster with 60 cores within about 2 weeks. This turn around time is considered fast enough to meet design phase requirements, and in validation, it also compares favorably to that required to hand-match a FEA model to engine test data, which is typically several months. [DOI: 10.1115/1.4003242]

A systematic CFD investigation was conducted to assess the core zone (CZ) casing heat transfer of a large civil aircraft engine. Three key engine operating conditions, maximum takeoff (MTO), cruise (CRZ) and ground idle (GI) were analyzed. Steady flows were assumed. Turbulence was simulated using the realizable k-epsilon model in conjunction with the scalable wall function. Buoyancy effect was taken into account. Radiation was calculated using the discrete ordinate (DO) model. It was shown that the forced convection heat transfer dominates in most of the casing surface in the core zone, and radiation is of second importance in general. However, in some areas where both convection and radiation heat transfer are weak but the latter is relatively greater in magnitude than the former, radiation heat transfer could thus become dominant. In addition, the overall impact of radiation on casing heat transfer increases from MTO to CRZ and GI conditions, as the strength of engine load decreases. The overall effect of buoyancy on casing heat transfer is small, but could be noticeable in some local areas where flow velocity is low. The insight into heat transfer features on the engine core zone casing supported by quantified CFD evidences is the first in the public domain, as far as authors are aware.

Computational fluid dynamics solutions are presented for unsteady flow and heat transfer in model fluid couplings. Factors studied include the effects of coupling size, cooling throughflow, vane numbers, and angled vanes. Predictions of torque characteristics are consistent with previously published experimental data and an elementary analysis. In this initial study, only single-phase solutions are presented, although these results do confirm that cavitation and/or air entrapment can be significant in practice. Angling of the vanes at 20 degrees to the axial direction is found to give a large increase in torque at low slip running conditions. However, pressure variations within the coupling are also increased and so the angled vane geometry will be more susceptible to cavitation.

An efficient finite element analysis/computational fluid dynamics (FEA/CFD) thermal coupling technique has been developed and demonstrated. The thermal coupling is achieved by an iterative procedure between FEA and CFD calculations. Communication between FEA and CFD calculations ensures continuity of temperature and heat flux. In the procedure, the FEA simulation is treated as unsteady for a given transient cycle. To speed up the thermal coupling, steady CFD calculations are employed, considering that fluid flow time scales are much shorter than those for the solid heat conduction and therefore the influence of unsteadiness in fluid regions is negligible. To facilitate the thermal coupling, the procedure is designed to allow a set of CFD models to be defined at key time points/intervals in the transient cycle and to be invoked during the coupling process at specified time points. To further enhance computational efficiency, a “frozen flow” or “energy equation only” coupling option was also developed, where only the energy equation is solved, while the flow is frozen in CFD simulation during the thermal coupling process for specified time intervals. This option has proven very useful in practice, as the flow is found to be unaffected by the thermal boundary conditions over certain time intervals. The FEA solver employed is an in-house code, and the coupling has been implemented for two different CFD solvers: a commercial code and an in-house code. Test cases include an industrial low pressure (LP) turbine and a high pressure (HP) compressor, with CFD modeling of the LP turbine disk cavity and the HP compressor drive cone cavity flows, respectively. Good agreement of wall temperatures with the industrial rig test data was observed. It is shown that the coupled solutions can be obtained in sufficiently short turn-around times (typically within a week) for use in design.

In compressor inter-disc cavities with a central axial throughflow it is known that the flow and heat transfer is strongly affected by buoyancy in the centrifugal force field. As a step towards developing CFD methods for such flows, buoyancy-driven flows under gravity in a closed cube and under centrifugal force in a sealed rotating annulus have been studied. Numerical simulations are compared with the experimental results of Kirkpatrick and Bohn (1986) and Bohn et al (1993). Two different CFD codes have been used and are shown to agree for the stationary cube problem. Unsteady simulations for the stationary cube show good agreement with measurements of heat transfer, temperature fluctuations, and velocity fluctuations for Rayleigh numbers up to 2 × 10 . Similar simulations for the rotating annulus also show good agreement with measured heat transfer rates. The CFD results confirm Bohn et al's results, showing reduced heat transfer and a different Rayleigh number dependency compared to gravity-driven flow. Large scale flow structures are found to occur, at all Rayleigh numbers considered.

Reynolds-Averaged Navier-Stokes (RANS) computations have been conducted to investigate the flow and heat trans-fer between two co-rotating discs with an axial throughflow of cooling air and a radial bleed introduced from the shroud. The computational fluid dynamics (CFD) models have been cou-pled with a thermal model of the test rig, and the predicted metal temperature compared with the thermocouple data. CFD solutions are shown to vary from a buoyancy driven regime to a forced convection regime, depending on the radial inflow rate prescribed at the shroud. At a high radial inflow rate, the computations show an excellent agreement with the measured temperatures through a transient rig condition. At a low radial inflow rate, the cavity flow is destabilized by the thermal stratification. Good qualitative agreement with the measurements is shown, although a significant over-prediction of disc temperatures is observed. This is associated with under prediction of the penetration of the axial throughflow into the cavity. The mismatch could be the result of strong sensitivity to the prescribed inlet conditions, in addition to possible shortcomings in the turbulence modeling.

A triple slotted aerofoil following the Handley Page 44F design was tested at City University London T-2 wind tunnel. The model allowed the study of a fixed triple slotted wing as well as investigation of the effects of isolated slots at different locations along the chord. PIV measurements were performed within the chord Reynolds number range in between approximately 200,000-400,000. The model was tested at an angle of attack of 22o. Measurements of mean streamwise velocity, velocity fluctuations and shear stress were analysed. The study shows how an isolated slot is more favourable when it is placed closest to the leading edge, although slow moving fluid regions can still be found close to the trailing edge. Fully attached flow was only achievable by using all three slots. In addition, the fully slotted profile is shown to generate channel exit velocities in the order of 1.4U∞, which highly energise the boundary layer on the suction side.

A wall-modelled large-eddy simulation (WMLES) method previously validated against laboratory experiments is applied to a real engine disc cavity geometry with surface and air temperatures representative of maximum power conditions. An appropriate set of independent nondimensional parameters describing the problem is defined and the sensitivities to these parameters are investigated by independently varying each parameter in the WMLES. Effects of a change in disc temperature distribution and a reduction in radius of the downstream disc are also investigated. The flow and heat transfer mechanisms predicted are very similar to those found for the research rig configuration although rotating cavity flow structures with two or more lobes are found for the engine geometry rather than the single-lobed structures shown in (Gao and Chew, ASME J Eng Gas Turbines Power, 2022). The simulations are compared with an elementary model giving further insight into scaling of the flow and heat transfer with operating conditions. The model assumes a well-mixed core flow in the cavity with constant rothalpy, relates shroud heat transfer to that of natural convection under gravity for high Rayleigh number, and relates disc heat transfer to conduction across unsteady Ekman layers. An energy balance for the cavity is used to obtain an effective mass flow exchange rate between the axial throughflow and the disc cavity to the disc and shroud heat transfer and core temperature. The model is considered to give a useful basis for engineering calculations involving correlation and extrapolation of WMLES and experimental results.

The buoyancy-affected flow in rotating disk cavities, such as occurs in compressor disk stacks, is known to be complex and difficult to predict. In the present work, large eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS) solutions are compared to other workers’ measurements from an engine representative test rig. The Smagorinsky-Lilly model was employed in the LES simulations, and the RNG k- turbulence model was used in the RANS modeling. Three test cases were investigated in a range of Grashof number Gr=1.87 to 7.41 108 and buoyancy number Bo=1.65 to 11.5. Consistent with experimental observation, strong unsteadiness was clearly observed in the results of both models; however, the LES results exhibited a finer flow structure than the RANS solution. The LES model also achieved significantly better agreement with velocity and heat transfer measurements than the RANS model. Also, temperature contours obtained from the LES results have a finer structure than the tangential velocity contours. Based on the results obtained in this work, further application of LES to flows of industrial complexity is recommended.

Flow and heat transfer in axial compressor disc cavities involve strong interaction of axial throughflow at the disc bores with centrifugal buoyant flow in the cavities. This paper presents large eddy simulation (LES) of flow and heat transfer in rotating cavities with a heated shroud and a relatively weak axial cooling throughflow. The conditions considered for a single cavity configuration correspond to Rossby numbers Ro=0.2 and 0.3, rotational Reynolds numbers Re Ω =3.2×10 5 and 7.7×10 5 , and buoyancy parameters βΔT=0.24 and 0.26. Reasonable agreement of the results with shroud heat transfer measurements was confirmed for the Ro=0.2 condition for which test data were available. A dual cavity configuration for Ro=0.3 and Re Ω =3.2×10 5 is also modelled. The simulations show that, at low Ro conditions, flow reversals occur along the length of the bore flow path, upstream and downstream of the rotating cavities. With the dual cavity strong, unsteady interactions between the flows in the two cavities occur. These flow interactions result in less stable flow structures, higher air temperatures within the cavities and lower shroud and disc heat transfer compared to the single cavity case. FFT analysis reveals a complex phase-locking mechanism between flows in the two cavities.

The internal gear box (IGB) of an aeroengine represents a severe challenge in computational fluid dynamics (CFD). In the present study, an axisymmetric CFD model was assessed to investigate the complex internal air flow in an aeroengine IGB. All the non-axisymmetric components and geometry features inside the gear box, such as bearings, gears, bolts and slots, as well as the radial drive system and vent pipes, were simulated using porous media models. Their flow resistance was estimated either by empirical correlations or by preparatory CFD studies and comparison with measurements. To evaluate the CFD technique adopted in the present investigation, a separate bolt windage study was conducted using a similar axisymmtric CFD model with the porous media approach. Good agreement of the bolt windage with other workers' rig test data was observed. The present application of the porous media approach into a complex gear box flow represents a first attempt to use state of art CFD to assist an industrial design. Both maximum take-off (MTO) and ground idle (GI) running conditions were investigated. The complex flow patterns in the gear box were obtained. The results show a similar dimensionless performance of intermediate pressure (IP) and high pressure (HP) gears between the two operating conditions. For the present gear box arrangement under investigation, the CFD results suggest that the airflows induced by the HP gear and HP bearing are higher than their IP counterparts. A comparison with power absorption rig test data for the similar HP crownwheel in isolation shows that an assumption of pressure loss coefficient of 10 for the porous media of bevel gears may be appropriate, as the HP gear torque coefficient obtained in the CFD prediction is equal to 0.05, very close to its expected value. In addition, the effects of an assumed stationary IP gear and a large seal clearance on the HP gear performance were also investigated. The numerical results show that their impacts are insignificant, probably due to the strong pumping effects of the HP gear. Further discussion on the possible influence of the airflow on the oil motion within the gearbox and assistance to improve the traditional internal airflow models used for bearing chamber sealing analysis was also made. Three dimensional geometry modeling and inclusion of the oil phase are considered feasible. Such further investigations would aid the understanding of the interaction between the induced airflow due to the rotating components and oil motion, and their impact on oil scavenging behaviour and `windage' contribution to heat oil.