Numerical Investigation of Oleo-Pneumatic Shock Absorber: A Multifidelity Approach

A representative shock absorber geometry is developed based on the general guidelines available in the literature, and it is validated against experimental measurements from a drop test. Simulations are conducted using a multi-fidelity approach ranging from unsteady scale resolving three-dimensional simulations to dynamic system models. High fidelity simulations provide a detailed insight into the flow physics inside the shock absorber, as well as help calibrate and validate lower fidelity methods, under conditions for which no experimental measurements are available to achieve that purpose. On the other hand, lower fidelity methods are used to efficiently scan the design space and test the dependency of the shock absorber performance on the various design parameters, in addition to identifying parameter combinations that would be of interest to investigate using a high-fidelity approach

Numerical investigation of oleo-pneumatic shock absorber: a multi-fidelity approach

A representative shock absorber geometry is developed based on the general guidelines available in the literature, and it is validated against experimental measurements from a drop test. Simulations are conducted using a multi-fidelity approach ranging from unsteady scale resolving three-dimensional simulations to dynamic system models. High fidelity simulations provide a detailed insight into the flow physics inside the shock absorber, as well as help calibrate and validate lower fidelity methods, under conditions for which no experimental measurements are available to achieve that purpose. On the other hand, lower fidelity methods are used to efficiently scan the design space and test the dependency of the shock absorber performance on the various design parameters, in addition to identifying parameter combinations that would be of interest to investigate using a high-fidelity approach

Numerical Investigation of Oleo-Pneumatic Shock Absorber: Setup and Validation

The simulation of an oleo-pneumatic shock absorber is discussed focusing on the solver validation and high fidelity case setup. The multi-physics nature of the problem is tackled by conducting a range of validation cases in the base areas expected to be of relevance. A dynamic system model of the shock absorber is used to generate physically consistent boundary conditions. In addition, steady RANS simulations provide a preliminary insight into the internal flow development and to assist in the design of higher resolution grids

Numerical investigation of orifice nearfield flow development in oleo-pneumatic shock absorbers

The flow field development through a simplified shock absorber orifice geometry is investigated using a single phase Large Eddy Simulation. Hydraulic oil is used as the working fluid with a constant inlet velocity and an open top boundary to allow the study to focus on the free shear layer and the flow development in the vicinity of the main orifice. The flow field is validated using standard mixing layer dynamics. The impact of the orifice shape is discussed with regards to the initial free shear layer growth, boundary layer development and the potential appearance of cavitation bubbles. Observations are made regarding the presence of flow field disturbances upstream of and through the orifice, thereby, leading to a notable turbulence intensity level in those regions.Innovate UK: 263261 and Airbus U

Numerical investigation of oleo-pneumatic shock absorber: setup and validation

The simulation of an oleo-pneumatic shock absorber is discussed focusing on the solver validation and high fidelity case setup. The multi-physics nature of the problem is tackled by conducting a range of validation cases in the base areas expected to be of relevance. A dynamic system model of the shock absorber is used to generate physically consistent boundary conditions. In addition, steady RANS simulations provide a preliminary insight into the internal flow development and to assist in the design of higher resolution grids

Unsteady multiphase simulation of oleo-pneumatic shock absorber flow

The internal flow in oleo-pneumatic shock absorbers is a complex multiphysics problem combining the interaction between highly unsteady turbulent flow and multiphase mixing, among other effects. The aim is to present a validated simulation methodology that facilitates shock absorber performance prediction by capturing the dominant internal flow physics. This is achieved by simulating a drop test of approximately 1 tonne with an initial contact vertical speed of 2.7 m/s, corresponding to a light jet. The flow field solver is ANSYS Fluent, using an unsteady two-dimensional axisymmetric multiphase setup with a time-varying inlet velocity boundary condition corresponding to the stroke rate of the shock absorber piston. The stroke rate is calculated using a two-equation dynamic system model of the shock absorber under the applied loading. The simulation is validated against experimental measurements of the total force on the shock absorber during the stroke, in addition to standard physical checks. The flow field analysis focuses on multiphase mixing and its influence on the turbulent free shear layer and recirculating flow. A mixing index approach is suggested to facilitate systematically quantifying the mixing process and identifying the distinct stages of the interaction. It is found that gas–oil interaction has a significant impact on the flow development in the shock absorber’s upper chamber, where strong mixing leads to a periodic stream of small gas bubbles being fed into the jet’s shear layer from larger bubbles in recirculation zones, most notably in the corner between the orifice plate and outer shock absorber wall.This research was funded by Innovate UK grant number 10002411, under the ATI/IUK Project: LANDOne, with Airbus UK as Industrial Lead

Hydroelectric powerplant intake structure numerical analysis

U radu se analizira dovodni sustav hidropostrojenja, njegove karakteristike i varijacije izvedbe. Budući da je hidroenergija značajniji i jedan od najstarijih izvora obnovljive i „čiste“ energije, iskorištavanje vodne energije se znatno razvilo od početaka do danas i stoga postoji široki spektar različitosti izvedbe u odnosu na potrebe postrojenja, vrstu postrojenja i geografske okolnosti. Detaljno se opisuje svaki od dijelova dovodnog sustava, njihova funkcija i način rada. Ovaj rad se prvenstveno bavi akumulacijskim hidroelektranama, njihovim dovodnim sustavima i analizom strujanja kroz iste. Nastavak završnog rada usmjeren je na numeričke modele kojima se opisuju strujanja i prijelazne pojave u cjevovodu. Od prijelaznih pojava u cjevovodima najznačajniji je hidraulički udar koji može uzrokovati velike negativne posljedice u hidropostrojenju i njegovoj okolnosti. U radu se opisuje numerički model idealnog hidrauličkog udara i opisuju se načini na koje se jednostavan model može proširiti. Opisane su jednadžba nestacionarnog strujanja - jednadžba kontinuiteta i jednadžba količine gibanja. Ostatak rada bavi se kreiranjem numeričkog modela hidrauličkog udara nastalog pri zatvaranju zasuna u crpnoj hidroelektrani „Fužine“. Simulacija je napravljena u komercijalnim programima AFT Fathom i AFT Impulse. Usporedbom dobivenih rezultata s vrijednostima mjerenim u samom dovodnom sustavu CHE „Fužine“ zaključuje se zadovoljavajuća kvaliteta prikazivanja stvarnosti izrađenog numeričkog modela.This paper analyzes the hydro power plant supply system, it's characteristics and variations of implementation. Being that hydropower is one of the most important and oldest sources of clean and renewable energy, the usage of water energy has considerably evolved since it's beginnings till today and hence there is a wide spectrum of different supply system types considering the plant's needs, type, and geographical situation. Power plant supply system elements are described in detail, as well as their function within the system and method of operation. This paper pimarily focuses on hydro accumulation power plants, their supply systems and flow analysis through the system. The continuation of this paper focuses on numerical models which describe fluid flow and hydraulic transients in the conduit. Water hammer is the most significant of hydraulic transients since it can cause great negative consequences within the power plant and in it's vicinity. Basic water hammer equations are derived and wave propagation is explained in detail. This paper also describes the transient flow equations. The rest of the paper is focused on creating a numerical model of water hammer in hydro power plant „Fužine“, which occurs while closing the shutter in the supply system. The simulation is made using the commercial computer programs AFT Fathom and AFT Impulse. The comparison of the numerical model with the data measured on site concludes that the quality of the numerical model is sastisfying

Hydroelectric powerplant intake structure numerical analysis

U radu se analizira dovodni sustav hidropostrojenja, njegove karakteristike i varijacije izvedbe. Budući da je hidroenergija značajniji i jedan od najstarijih izvora obnovljive i „čiste“ energije, iskorištavanje vodne energije se znatno razvilo od početaka do danas i stoga postoji široki spektar različitosti izvedbe u odnosu na potrebe postrojenja, vrstu postrojenja i geografske okolnosti. Detaljno se opisuje svaki od dijelova dovodnog sustava, njihova funkcija i način rada. Ovaj rad se prvenstveno bavi akumulacijskim hidroelektranama, njihovim dovodnim sustavima i analizom strujanja kroz iste. Nastavak završnog rada usmjeren je na numeričke modele kojima se opisuju strujanja i prijelazne pojave u cjevovodu. Od prijelaznih pojava u cjevovodima najznačajniji je hidraulički udar koji može uzrokovati velike negativne posljedice u hidropostrojenju i njegovoj okolnosti. U radu se opisuje numerički model idealnog hidrauličkog udara i opisuju se načini na koje se jednostavan model može proširiti. Opisane su jednadžba nestacionarnog strujanja - jednadžba kontinuiteta i jednadžba količine gibanja. Ostatak rada bavi se kreiranjem numeričkog modela hidrauličkog udara nastalog pri zatvaranju zasuna u crpnoj hidroelektrani „Fužine“. Simulacija je napravljena u komercijalnim programima AFT Fathom i AFT Impulse. Usporedbom dobivenih rezultata s vrijednostima mjerenim u samom dovodnom sustavu CHE „Fužine“ zaključuje se zadovoljavajuća kvaliteta prikazivanja stvarnosti izrađenog numeričkog modela.This paper analyzes the hydro power plant supply system, it's characteristics and variations of implementation. Being that hydropower is one of the most important and oldest sources of clean and renewable energy, the usage of water energy has considerably evolved since it's beginnings till today and hence there is a wide spectrum of different supply system types considering the plant's needs, type, and geographical situation. Power plant supply system elements are described in detail, as well as their function within the system and method of operation. This paper pimarily focuses on hydro accumulation power plants, their supply systems and flow analysis through the system. The continuation of this paper focuses on numerical models which describe fluid flow and hydraulic transients in the conduit. Water hammer is the most significant of hydraulic transients since it can cause great negative consequences within the power plant and in it's vicinity. Basic water hammer equations are derived and wave propagation is explained in detail. This paper also describes the transient flow equations. The rest of the paper is focused on creating a numerical model of water hammer in hydro power plant „Fužine“, which occurs while closing the shutter in the supply system. The simulation is made using the commercial computer programs AFT Fathom and AFT Impulse. The comparison of the numerical model with the data measured on site concludes that the quality of the numerical model is sastisfying

Hydroelectric powerplant intake structure numerical analysis

U radu se analizira dovodni sustav hidropostrojenja, njegove karakteristike i varijacije izvedbe. Budući da je hidroenergija značajniji i jedan od najstarijih izvora obnovljive i „čiste“ energije, iskorištavanje vodne energije se znatno razvilo od početaka do danas i stoga postoji široki spektar različitosti izvedbe u odnosu na potrebe postrojenja, vrstu postrojenja i geografske okolnosti. Detaljno se opisuje svaki od dijelova dovodnog sustava, njihova funkcija i način rada. Ovaj rad se prvenstveno bavi akumulacijskim hidroelektranama, njihovim dovodnim sustavima i analizom strujanja kroz iste. Nastavak završnog rada usmjeren je na numeričke modele kojima se opisuju strujanja i prijelazne pojave u cjevovodu. Od prijelaznih pojava u cjevovodima najznačajniji je hidraulički udar koji može uzrokovati velike negativne posljedice u hidropostrojenju i njegovoj okolnosti. U radu se opisuje numerički model idealnog hidrauličkog udara i opisuju se načini na koje se jednostavan model može proširiti. Opisane su jednadžba nestacionarnog strujanja - jednadžba kontinuiteta i jednadžba količine gibanja. Ostatak rada bavi se kreiranjem numeričkog modela hidrauličkog udara nastalog pri zatvaranju zasuna u crpnoj hidroelektrani „Fužine“. Simulacija je napravljena u komercijalnim programima AFT Fathom i AFT Impulse. Usporedbom dobivenih rezultata s vrijednostima mjerenim u samom dovodnom sustavu CHE „Fužine“ zaključuje se zadovoljavajuća kvaliteta prikazivanja stvarnosti izrađenog numeričkog modela.This paper analyzes the hydro power plant supply system, it's characteristics and variations of implementation. Being that hydropower is one of the most important and oldest sources of clean and renewable energy, the usage of water energy has considerably evolved since it's beginnings till today and hence there is a wide spectrum of different supply system types considering the plant's needs, type, and geographical situation. Power plant supply system elements are described in detail, as well as their function within the system and method of operation. This paper pimarily focuses on hydro accumulation power plants, their supply systems and flow analysis through the system. The continuation of this paper focuses on numerical models which describe fluid flow and hydraulic transients in the conduit. Water hammer is the most significant of hydraulic transients since it can cause great negative consequences within the power plant and in it's vicinity. Basic water hammer equations are derived and wave propagation is explained in detail. This paper also describes the transient flow equations. The rest of the paper is focused on creating a numerical model of water hammer in hydro power plant „Fužine“, which occurs while closing the shutter in the supply system. The simulation is made using the commercial computer programs AFT Fathom and AFT Impulse. The comparison of the numerical model with the data measured on site concludes that the quality of the numerical model is sastisfying