@article{
	11589_8853,
	author = { LIPPOLIS A.},
	title = {Analytical study and optimization of power shift drives},
	year = {9999},
	journal = {ENERGY CONVERSION AND MANAGEMENT}
}
@article{
	11589_77183,
	author = { Fornarelli  F  and  Lippolis  A  and  Oresta  P },
	title = {Buoyancy effect on the flow pattern and the thermal performance of an array of circular cylinders},
	year = {9999},
	journal = {JOURNAL OF HEAT TRANSFER},
	abstract = {In this paper we found, by means of numerical simulations,
a transition in the oscillatory character of the flow field for a
particular combination of buoyancy and spacing in an array
of six circular cylinders at a Reynolds number of 100 and
Prandtl number of 0:7. The cylinders are iso-thermal and
they are aligned with the Earth acceleration (g). According
to the array orientation, an aiding or an opposing buoyancy
is considered. The effect of natural convection with respect
to the forced convection is modulated with the Richardson
number, Ri, ranging between 1 and 1. Two values of center
to center spacing (s = 3:6d 4d) are considered. The
effects of buoyancy and spacing on the flow pattern in the
near and far field are described. Several transitions in the
flow patterns are found and a parametric analysis of the dependence
of the force coefficients and Nusselt number with
respect to the Richardson number is reported. For Ri = 1,
the change of spacing ratio from 3:6 to 4 induces a transition
in the standard deviation of the force coefficients and
heat flux. In fact the transition occurs due to rearrangement
of the near field flow in a more ordered wake pattern. Therefore,
attention is focused on the influence of geometrical and
buoyancy parameters on the heat and momentum exchange
and their fluctuations. The available heat exchange models
for cylinders array provide a not accurate prediction of the
Nusselt number in the cases here studied.}
}
@article{
	11589_77182,
	author = { Posa  Antonio  and  Lippolis  Antonio  and  Balaras  Elias },
	title = {Investigation of Separation Phenomena in a Radial Pump at Reduced Flow Rate by Large-Eddy Simulation},
	year = {2016},
	journal = {JOURNAL OF FLUIDS ENGINEERING},
	volume = {138},
	abstract = {Turbopumps operating at reduced flow rates experience significant separation and backflow phenomena. Although Reynolds-Averaged Navier–Stokes (RANS) approaches proved to be usually able to capture the main flow features at design working conditions, previous numerical studies in the literature verified that eddy-resolving techniques are required in order to simulate the strong secondary flows generated at reduced loads. Here, highly resolved large-eddy simulations (LES) of a radial pump with a vaned diffuser are reported. The results are compared to particle image velocimetry (PIV) experiments in the literature. The main focus of the present work is to investigate the separation and backflow phenomena occurring at reduced flow rates. Our results indicate that the effect of these phenomena extends up to the impeller inflow: they involve the outer radii of the impeller vanes, influencing significantly the turbulent statistics of the flow. Also in the diffuser vanes, a strong spanwise evolution of the flow has been observed at the reduced load, with reverse flow, located mainly on the shroud side and on the suction side (SS) of the stationary channels, especially near the leading edge of the diffuser blades.},
	keywords = {Impellers , Diffusers , Design , Flow (Dynamics) , Blades , Separation (Technology) , Pumps , Turbulence},
	doi = {10.1115/1.4033843},	
	pages = {121101--121113}
}
@article{
	11589_5555,
	author = { Posa A  and  Lippolis A  and  Balaras E },
	title = {Large-eddy simulation of a mixed-flow pump at off-design conditions},
	year = {2015},
	journal = {JOURNAL OF FLUIDS ENGINEERING},
	volume = {137},
	abstract = {The flow through turbopumps is characterized by highly unsteady phenomena at part load conditions, involving large separation and generation of vortical structures. This behavior is strongly dependent on the interaction between rotating and steady parts, which is significantly modified, compared to the one at the design flow rate. Therefore, at off-design conditions, eddy-resolving computations are more suitable to analyze the complex physics occurring inside turbomachinery channels. In this work the large eddy simulation (LES), coupled with an immersed-boundary (IB) method, is utilized to study a mixed-flow pump at a reduced flow rate, equivalent to 40% of the nominal one. The present approach has been already validated in a previous study, where a satisfactory agreement with two-dimensional (2D) particle image velocimetry (PIV) experiments has been shown at design conditions. In this paper a comparison with the LES results at the optimal flow rate is also proposed, in order to understand the important modifications of the flow occurring at part loads.},
	keywords = {Machine design; Off design condition; Unsteady phenomena; Immersed boundary; Large eddy simulation; Turbulent flow},
	doi = {10.1115/1.4030489},	
}
@article{
	11589_471,
	author = { Fornarelli F  and  Oresta P  and  Lippolis A },
	title = {Flow patterns and heat transfer around six in-line circular cylinders at low Reynolds number},
	year = {2015},
	journal = {JP JOURNAL OF HEAT AND MASS TRANSFER},
	volume = {11},
	abstract = {The flow field and the heat transfer around six in-line iso-thermal circular cylinders have been studied by means of numerical simulations. Two values of the center to center spacing \"\" and 4d, where dis the cylinder diameter) at Reynolds number of 100 and Prandtl number of 0.7 have been investigated. Similarly to the in-line two cylinders configuration, in this range, a transition in the flow and in the heat transfer occurs. Two different flow patterns have been identified: the stable shear layer (SSL) mode and the shear layer secondary vortices (SLSV) mode, at 3.6 and 4 spacing ratios respectively. At \"\" the flow pattern causes the entrainment of cold fluid on the downstream cylinders enhancing the heat transfer.  On the other hand, at \"\" two stable opposite shear layers prevent the cold fluid entrainment over the downstream cylinders reducing their heat exchange. The overall time average heat transfer of the array is enhanced up to 25% decreasing the spacing ratio from 4 to 3.6. Furthermore, it is found that the increased heat transfer is related to the phase shift between the Nusselt time series of successive cylinders.},
	keywords = {Forced convection; Low Reynolds number; DNS},
	url = {http://www.pphmj.com/abstract/8891.htm},
	doi = {http://dx.doi.org/10.17654/JPHMTFeb2015_001_028},	
	pages = {1--28}
}
@conference{
	11589_21757,
	author = { Fornarelli F  and  Oresta P  and  Lippolis A },
	title = {Wake interference effects on the heat transfer enhancement around a row of circular cylinders},
	year = {2014},
	booktitle = {Proceedings of 10th European Fluid Mechanics Conference},
	abstract = {The numerical simulations of the heat transfer around an array of isothermal circular cylinders immersed in a
stream has been carried out solving the two-dimensional Navier-Stokes equations. The cylinders have been
placed in a single row configuration aligned with the free stream velocity at Reynolds number 100 and Prandtl
number 0.7.
In Fig.1 it is shown the instantaneous temperature distribution for the case of six in-line circular cylinders at
spacing ratio (s/d) equal to 4 and 3.6, where s is the center-to-center cylinder spacing and d is the cylinder
diameter.
In the latter case, a transition in the flow patterns occurs with the flow organized in a vortex shedding
responsible for the entrainment of cold fluid in the gaps. This phenomenon makes stronger the thermal gradient
close to the cylinders leading the heat transfer enhancement with the Nusselt number 25 % higher respect to the
case at s/d=4.
Furthermore a frequency analysis of the time dependent Nusselt number, Nui, at the i-th cylinder, shows that
the main frequency is the same for all the cylinders.
We found evidences that the signature of the heat transfer enhancement could be related to the phase shift
between two successive cylinders (i+1- i), where the phase shift (i) is defined as the difference between the
phase of each main harmonic component of the Nui respect to the phase of the signal at the first cylinder.}
}
@conference{
	11589_18430,
	author = { Fornarelli F  and  Oresta P  and  Lippolis A },
	title = {Flow transitions around in line cylinders},
	year = {2014},
	booktitle = {Proceedings of 1st  Workshop SCORE@POLIBA},
	abstract = {The flow around aligned cylinders is an archetype for several
industrial devices (rod structure of the nuclear reactors, compact heat
exchangers for electronic components, pin-fins heat exchangers for
micro-devices ) and environmental phenomena (diffusion process close to the
vegetation). Cylinders produce instabilities in the flow structures that are very
sensitive to the control parameters such as the inflow velocity, the spacing
between the cylinders and the fluid viscosity. The instabilities leads the
transport phenomena close to the cylinders and they affect the force, the
thermal balance at their surface and the diffusion process. The strong velocity
gradients in confined spaces make that the experimental analysis is difficult,
while the numerical simulation appears to be a promising tool for this purpose.},
	keywords = {Fluid dynamics; Bluff bodies; Wake interference}
}
@conference{
	11589_18396,
	author = { Fortunato B  and  Lippolis A  and  Vacca G  and  Amirante  R  and  Camporeale S M  and  Dambrosio  and  Oresta P  and  Torresi M  and  Fornarelli F },
	title = {Activities of the research group on  energy efficiency and renewable energy},
	year = {2014},
	publisher = {Gangemi},
	address = {ROMA},
	volume = {B},
	booktitle = {Groups mResearch on KERTS and SCS -
1st Workshop on the State of the Art and Challenges of Research Efforts of POLIBA},
	keywords = {Energy ; Renewable; Efficiency},
	pages = {173--177}
}
@conference{
	11589_22930,
	author = { Posa A  and  Lippolis A  D  and  Balaras E },
	title = {Large-eddy simulations of a mixed-flow pump at off-design conditions},
	year = {2014},
	booktitle = {Proceedings of 67th Annual Meeting of the APS Division of Fluid Dynamics},
	abstract = {reduced flow-rates in turbopumps produce significant unsteady phenomena, characterized by separation and back-flow. In this study an LES approach coupled with an immersed-boundary methodology is utilized to investigate the changes in the flow physics, when compared to nominal flow-rates. The present methodology has been already validated for the design case through comparison with PIV experiments in the literature. It will be shown that for a reduced flow rate (40\% of the design one) separation phenomena are generated on the suction side of the rotor blades and on the pressure side of the stator ones. Significant spanwise non-uniformity is produced in the diffuser channels, with a displacement of the flow towards the hub side and back-flow on the shroud side. The values of turbulent kinetic energy are increased by an order of magnitude at off-design conditions and the main source of turbulence is not anymore the flow from the suction side and the trailing edge of the rotor blades: most turbulence is generated now at the leading edge of the diffuser blades. The increased interaction between rotating and stationary parts implies also a stronger dependence of the flow features on the relative position between impeller and diffuser blades.},
	url = {http://meetings.aps.org/link/BAPS.2014.DFD.R25.8}
}
@article{
	11589_8053,
	author = { Stefanizzi P  and  Lippolis A  and  Liuzzi S },
	title = {Experimental and numerical analysis of heat transfer in the cavities of hollow blocks},
	year = {2013},
	journal = {INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY},
	volume = {31},
	abstract = {Given the importance of the assessment of the insulation performance of the building envelope in the context of energy certification of buildings, a detailed analysis of the reliability of the methods of evaluation of heat transfer in the air cavities of hollow blocks has been carried out.
An experimental study was conducted in the laboratory. Heat transfer measurements on specimens with parallelepiped cavities were done, through a guarded hot plate device according to UNI EN 12664. A numerical analysis of the heat transfer in the specimens through the software ANSYS FLUENT was carried out.
The analysis of the numerical and experimental results when compared with the predictions obtained from simplified models of technical standards, have called attention to the order of magnitude of the calculation accuracy obtainable with such procedures. For some geometric configurations and boundary conditions, the application of the standards can lead to large errors of evaluation of the thermal resistance of the cavity.},
	keywords = {Energy certification; Experimental and numerical analysis; Heat transfer measurements},
	pages = {149--154}
}
@conference{
	11589_25188,
	author = { Stefanizzi P  and  Lippolis A  and  Liuzzi S },
	title = {ANALISI NUMERICA E SPERIMENTALE DELLA TRASMISSIONE DEL CALORE NELLE CAVITA’ D’ARIA DEI BLOCCHI FORATI},
	year = {2013},
	booktitle = {Atti del 7° Congresso Nazinale AIGE},
	abstract = {The thermal performance of hollow bricks, as elements of the building envelope, is mainly linked to the presence of air cavities. The heat propagates within those components through the three basic modes of transmission: conduction in the solid matrix, convection of the air cavity, direct radiation between surfaces that face in the cavities.
The rigorous treatment of such heat exchange is very complex even in thermal conditions close to the environment with moderate temperature differences. In engineering practice a simplified calculation method is used, as incorporated in national and international standards, which reduce heat transfer into the cavity to an equivalent heat conduction that results in the transport of the same thermal power.
UNI EN ISO 6946 and UNI 10355 follow this method by proposing a simplified model of computation that lead to different results.
Given the importance that the correct assessment of the insulation performance of the envelop in the context of energy certification of buildings it was considered useful to undertake a detailed analysis of the reliability of the estimation methods of heat transfer in air cavities of hollow bricks.
The study was conducted with the use of different tools, numerical and experimental. An experimental study was conducted in the laboratory with heat transmission measurements, in specimens with parallelepiped cavities, through the guarded hot plate apparatus according to UNI EN 12664.
The analysis of the results, numerical and experimental, compared with the predictions obtained from simplified models of technical standards, have called attention to the order of magnitude of the calculation accuracy obtainable with such procedures. For certain geometric configurations and boundary conditions, the application of the standard procedures can lead to large errors of evaluation of the thermal resistance of the cavity.},
	keywords = {Blocchi forati; trasmissione del calore; Ansys-Fluent}
}
@article{
	11589_52143,
	author = { Posa A  and  Oresta P  and  Lippolis A },
	title = {Influence of the Spool Velocity on The Performance of a Directional Hydraulic Valve},
	year = {2013},
	journal = {INTERNATIONAL JOURNAL OF FLUID POWER},
	volume = {14},
	abstract = {In this paper an accurate numerical method has been used to verify the influence of the spool velocity on the performance
of a directional hydraulic valve (4/3, closed center): the flow during the opening phase of the valve has been
solved by Direct Numerical Simulation (DNS), using an Immersed-Boundary (IB) technique.
The present results have been compared with the ones of a previous study, based on the same numerical method, but
with a stationary spool. The numerical comparisons prove that the "quasi-stationary" hypothesis is approximately correct
for present commercial devices, but it is not suitable for future high-speed valves. However it is shown that, even
inside the range of the spool velocities currently adopted, for small pressure drops Δp and small openings s more significant
differences arise on the axial forces.},
	keywords = {Direct Numerical Simulation, Directional hydraulic valves, Finite-difference methods, Immersed-Boundary methods},
	doi = {10.1080/14399776.2013.10801410},	
	pages = {15--25}
}
@article{
	11589_52200,
	author = { AMIRANTE R  and  LIPPOLIS A  and  TAMBURRANO P },
	title = {Theoretical and Experimental Analysis of a Coupled System Proportional Control Valve and Hydraulic Cylinder},
	year = {2013},
	journal = {UNIVERSAL JOURNAL OF ENGINEERING SCIENCE}
}
@article{
	11589_1090,
	author = { Posa A  and  Oresta P  and  Lippolis A },
	title = {Analysis of a directional hydraulic valve by a direct numerical simulation
using an immersed-boundary method},
	year = {2013},
	journal = {ENERGY CONVERSION AND MANAGEMENT},
	volume = {65},
	abstract = {The improvement of the hydraulic valves depends on the careful analysis
of the coherent structures driving the motion of the working fluid. In the
past those devices have been studied by experimental tests; during the last
15 years also several numerical works have been presented, solving the flow
on body-fitted computational grids by RANS methods.
In this study a different approach is proposed for the axisymmetric analysis
of a directional valve (4/3, closed centre): whereas the RANS techniques are
based on the time-averaged equations of the flow, in the present work the unsteady Navier-Stokes equations have been solved using the Direct Numerical
Simulation (DNS); the time evolution of the physics is simulated, providing
important details on the instantaneous structures of the flow, affecting the valve performance. Furthermore, while in the previous numerical studies the
computational domain has been discretized by conformal grids, in this case
the fluid-body interaction has been represented by an immersed-boundary
(IB) method on a Cartesian grid, more suitable for unsteady eddy-resolving
simulations, as DNS.
The analysis of the discharge coefficient and the flow forces for different openings s and pressure drops ∆p is presented in this paper. The behaviour of
those global parameters is justified also considering the time-averaged and
the instantaneous fields. For small openings and pressure drops the flow is
steady and attached to the wall of the discharge chamber on the side of the
restricted section. When s and ∆p are increased the jet separates at the restricted section and it re-attaches downstream (Coanda effect), keeping the
steady state. Finally, for large openings and pressure drops the flow becomes
strongly unsteady: it is organized like a free jet and is dominated by large
vortices.},
	keywords = {Direct Numerical Simulation; Directional hydraulic valves; Immersed-Boundary methods},
	doi = {10.1016/j.enconman.2012.07.012},	
	pages = {497--506}
}
@article{
	11589_51933,
	author = { Posa A  and  Oresta P  and  Lippolis A },
	title = {Simulazione diretta del flusso in un distributore
oleodinamico mediante un metodo ai contorni immersi.
Direct Numerical Simulation on a directional hydraulic valve by an immersed-boundary method.},
	year = {2012},
	journal = {LA TERMOTECNICA},
	volume = {LXVI},
	abstract = {"In this paper a directional valve (4\/3, closed center) is analyzed using a code based on the immersed boundary method and solving the Navier-. Stokes equations by a Direct Numerical Simulation (DNS).. The results are presented in terms of instantaneous and time-averaged fields, showing the Coanda effect for small valve openings, and global parameters,. such as the discharge coefficient and the flow force coefficient K."},
	pages = {53--56}
}
@conference{
	11589_52601,
	author = { Rubino G  and  Fornarelli F  and  Lippolis A  and  Oresta P },
	title = {Fluid dynamic optimization of internal flow in a wind turbine nacelle},
	year = {2012},
	booktitle = {67° Congresso Nazionale ATI}
}
@inbook{
	11589_11777,
	author = { LIPPOLIS A.},
	title = {LE TRASMISSIONI POWER SHIFT
PER TRATTRICI AGRICOLE},
	year = {2011},
	publisher = {Edizioni Artestampa},
	address = {Modena},
	booktitle = {Soluzioni Innovative per la riduzione del Consumo Energetico di Circuiti Idraulici per Trattrici Agricole},
	pages = {60--73}
}
@conference{
	11589_52705,
	author = { POSA A  and  ORESTA P  and  LIPPOLIS A },
	title = {Simulazione diretta del Flusso in un Distributore Oleodinamico mediante un Metodo ai Contorni Immersi},
	year = {2011},
	booktitle = {Atti del 66° Congresso ATI}
}
@article{
	11589_2612,
	author = { POSA A  and  LIPPOLIS A  and  VERZICCO R  and  BALARAS E },
	title = {Large-eddy simulations in mixed-flow pumps using an immersed-boundary method},
	year = {2011},
	journal = {COMPUTERS & FLUIDS},
	volume = {47},
	abstract = {Computations of turbulent and transitional flows in rotating machinery applications are very challenging due to complexity of the geometry, which usually consists of multiple rotating and stationary parts. The application of well-established, body-fitted methods frequently utilizes overset grids and different reference frames, which have an adverse impact on the overall accuracy and cost-efficiency of the method. In the present work we explore the feasibility of performing computations of such flows using a single reference frame and an immersed-boundary approach. In particular, we report one of the first large-eddy simulation in this class of flows, where a structured cylindrical coordinate solver with optimal conservation properties is utilized in conjunction with an immersed-boundary method. To evaluate the accuracy of the computations the results are compared to the experimental measurements in [1]. Results using the standard Smagorinsky model and the Filtered Structured Function model are presented. We demonstrate that the overall approach is well suited for the flow under consideration and the results with the more advanced subgrid scale model are in good agreement with the experiment. We also briefly discuss some of the features of the instantaneous flow dynamics, to provide a glimpse of the wealth of information that can be extracted from such computations.},
	keywords = {Computational fluid dynamics; Turbomachinery ; Large eddy simulation},
	doi = {10.1016/j.compfluid.2011.02.004},	
	pages = {33--43}
}
@conference{
	11589_14578,
	author = { LIPPOLIS A  and  CERFEDA S },
	title = {OTTIMIZZAZIONE ENERGETICA DI TRASMISSIONI POWER SHIFT PER TRATTRICI AGRICOLE},
	year = {2010},
	booktitle = {ATTI del 65° Congresso Nazionale ATI}
}