Numerical Simulation of Fluidic Thrust-Vectoring

The paper focuses on a computational method for the investigation of Fluidic Thrust Vectoring (FTV). Thrust vectoring in symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions and, therefore, the vectoring of the primary jet thrust. The methodology proposed here can be applied for studying numerically most of the strategies for fluidic thrust vectoring, as shock-vector control, sonic-plane skewing and the counterflow method. The computational technique is based on a well-assessed mathematical model. The flow governing equations are solved according to a finite volume discretization technique of the compressible RANS equations coupled with the Spalart-Allmaras turbulence model. Second order accuracy in space and time is achieved using an Essentially Non Oscillatory scheme. For validation purposes, the proposed numerical tool is used for the simulation of thrust vectoring based on the dual-throat nozzle concept. Nozzle performances and thrust vector angles are computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results obtained are compared with the experimental data available in the open literature

Thrust Vectoring of a Fixed Axisymmetric Supersonic Nozzle Using the Shock-Vector Control Method

The application of the Shock Vector Control (SVC) approach to an axysimmetric supersonic nozzle is studied numerically. SVC is a Fluidic Thrust Vectoring (FTV) strategy that is applied to fixed nozzles in order to realize jet-vectoring effects normally obtained by deflecting movable nozzles. In the SVC method, a secondary air flow injection close to the nozzle exit generates an asymmetry in the wall pressure distribution and side-loads on the nozzle, which are also lateral components of the thrust vector. SVC forcing of the axisymmetric nozzle generates fully three-dimensional flows with very complex structures that interact with the external flow. In the present work, the experimental data on a nozzle designed and tested for a supersonic cruise aircraft are used for validating the numerical tool at different flight Mach numbers and nozzle pressure ratios. Then, an optimal position for the slot is sought and the fully 3D flow at flight Mach number M∞=0.9 is investigated numerically for different values of the SVC forcing

ACTIVE FLOW CONTROL OF AN OVER-EXPANDED NOZZLE BY SHOCK VECTOR CONTROL

Thrust vectoring obtained by the nozzle flow manipulation technique known as Shock Vector Control (SVC) is investigated numerically. In the shock vector control method, a shock structure is generated in the main flow by using transversal continuous blowing. The pressure distribution on the nozzle walls becomes asymmetric, thus giving rise to a lateral force. The open-loop response of the nozzle and the thrust vectoring effectiveness/controllability are investigated by using a CFD tool based on the compressible URANS equations. Nozzle performances and thrust vector angles have been computed for different nozzle pressure ratios in the range of over-expanded conditions. The latter represent the worst case, where the shock structure generated by the control is amplified by the re-compression requirements imposed by the external ambient pressure

Numerical Simulation of a Vectored Axisymmetric Nozzle

A CFD based approach to the fully three-dimensional simulation of vectored nozzle is presented. The underlying tech- nology used is based on an active flow control technique known as Fluidic Thrust-Vectoring. The flow governing equations are solved by using a finite volume discretization of the compressible Unsteady RANS equations. The numerical results obtained are compared with the experimental data found in the open literature

Differential Throttling and Fluidic Thrust Vectoring in a Linear Aerospike

Aerospike nozzles represent an interesting solution for Single-Stage-To-Orbit or clustered launchers owing to their self-adapting capability, which can lead to better performance compared to classical nozzles. Furthermore, they can provide thrust vectoring in several ways. a simple solution consists of applying differential throttling when multiple combustion chambers are used. An alternative solution is represented by fluidic thrust vectoring, which requires the injection of a secondary flow from a slot. In this work, the flow field in a linear aerospike nozzle was investigated numerically and both differential throttling and fluidic thrust vectoring were studied.The flow field was predicted by solving the Reynolds-averaged Navier–Stokes equations. The thrust vectoring performance was evaluated in terms of side force generation and axial force reduction. The effectiveness of fluidic thrust vectoring was investigated by changing the mass flow rate of secondary flow and injection location. The results show that the response of the system can be non-monotone with respect to the mass flow rate of the secondary injection. In contrast, differential throttling provides a linear behaviour but it can only be applied to configurations with multiple combustion chambers. Finally, the effects of different plug truncation levels are discussed

Numerical and Experimental Assessment of a Linear Aerospike

In the present work a linear aerospike nozzle model has been studied with cold flow experiments in various working conditions. A series of numerical 3D RANS simulations have been performed in order to directly compare numerical and experimental results. Mean pressure distributions have been measured on the nozzle model symmetry plane, in order to characterize the flow evolution along the walls of the plug. The presented results show a good agreement between numerical and experimental results

Is Serum Cystatin C a Sensitive Marker of Glomerular Filtration Rate (GFR)? A Preliminary Study on Renal Transplant Patients

Human cystatin C is a basic low molecular mass protein (13,359 Dalton) freely filtered through the glomerulus and almost completely re-absorbed and catabolized by proximal tubular cells. We measured serum cystatin C in 38 kidney transplant patients (23 males, 15 females) aged between 6 and 32 years. To assess renal function, serum and urinary creatinine were also determined in all patients, and creatinine clearance was finally calculated. Cystatin C was determined by a particle-enhanced turbidimetric assay, and creatinine was measured by gas chromatography-mass spectrometry. To compare the diagnostic efficiency of cystatin C with that of creatinine, inulin clearance was performed on 12 renal transplant patients, and receiver operating characteristic (ROC) analysis was applied. The results of this study demonstrate that serum cystatin C significantly increases in renal transplant patients with reduced creatinine clearance (70 mL/min per 1.73 m2) and that the diagnostic accuracy of serum cystatin C is better than of serum creatinine. Cystatin C may be utilized as a very marker of reduced GFR

A viscous inverse method for aerodynamic design

A numerical technique to solve two-dimensional inverse problems that arise in aerodynamic design is presented. The approach, which is well-established for inviscid, rotational flows, is here extended to the viscous case. Two-dimensional and axisymmetric configurations are here considered. The solution of the inverse problem is given as the steady state of an ideal transient during which the flowfield assesses itself to the boundary conditions by changing the boundary contour. Comparisons with theoretical and experimental results are used to validate the numerical procedure

Impact of antimicrobial stewardship interventions on appropriateness of surgical antibiotic prophylaxis. How to improve

Background and Objectives: Surgical Site Infections (SSIs) are the most common healthcare-associated infections and represent a major clinical problem in terms of mortality, morbidity, length of stay and overall costs. The appropriateness of Surgical Antibiotic Prophylaxis (SAP) is a key component to reduce the SSIs while the inappropriateness is a major cause of some emerging infections and selection of antibiotic resistance, therefore increasing healthcare costs. For this reasons international and national guidelines have been developed to guide clinicians in the optimal use of SAP. The The overall compliance to these guidelines is poor, with a high heterogeneity and as a consequence there is no universally recognized intervention to improve the appropriateness of SAP. The antimicrobial stewardship program is a systematic approach to improve appropriateness of antimicrobial use, to optimize the treatment of infections and to minimize the adverse effects associated with antibiotic use, like antimicrobial resistance, toxicity and costs. We describe a successfully Antimicrobial Stewardship (AMS) intervention on SAP appropriateness. Material and Methods: The prospective study was conducted at “Santa Maria” tertiary hospital in Terni, Umbria, in 12 main surgical units and was organized in three subsequent phases . The hospital defined evidence-based guidelines for optimal use of SAP, approved a new workflow to optimize the process of ordering, dispensing, administering and documenting SAP and created a satellite pharmacy in the operative block . Phase 1: we analysed 2059 elective surgical cases from January to June 2018 for 3 SAP parameters of appropriateness: indication, choice, dose. Phase 2: in July 2018 an audit was performed to analyse the result ; we reviewed 1781 elective surgical procedures from July to December 2018 looking for the same 3 SAP parameters of appropriateness. Results: The comparative analysis between phase 1 and 2 has demonstrated that the correct indication has a significant improvement (p-value 0.00128), moving from 73.63% in phase 1 to 77.82% in phase 2. The choice of antibiotic has not shown any significant improvement (p-value 0.4863) . The correct dose significantly improved (p-value< 2.2 1016 ), rising from 71.75% in phase 1 to 86.19% in phase 2. The overall compliance had a significant improvement (p-value <5.6 1012) passing from 40.21% in tphase 1 to 51.15% in phase 2. Conclusions: Our prospective study demonstrated a model of succesfully antimicrobial stewardship intervention that improves appropriateness of SAP