Results of simulation and scaled flight tests performed on a rocket-plane at high angles of attack

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Agnieszka Kwiek ◽  
Cezary Galinski ◽  
Krzysztof Bogdański ◽  
Jaroslaw Hajduk ◽  
Andrzej Tarnowski
Keyword(s):  
Numerical Simulations ◽  
Software Package ◽  
Steep Descent ◽  
Flight Test ◽  
Full Scale ◽  
Scaled Model ◽  
Technical Problems ◽  
Content Type ◽  
Suborbital Flights ◽  
High Angles Of Attack

Purpose According to the study of the space flight market, there is a demand for space suborbital flights including commercial tourist flights. However, one of the challenges is to design a mission and a vehicle that could offer flights with relatively low G-loads. The project of the rocket-plane in a strake-wing configuration was undertaken to check if such a design could meet the FAA recommendation for this kind of flight. The project concept assumes that the rocket plane is released from a slowly flying carrier plane, then climbs above 100 kilometers above sea level and returns in a glide flight using a vortex lift generated by the strake-wing configuration. Such a mission has to include a flight transition during the release and return phases which might not be comfortable for passengers. Verification if FAA recommendation is fulfilled during these transition maneuvers was the purpose of this study. Design/methodology/approach The project was focused on the numerical investigation of a possibility to perform transition maneuvers mentioned above in a passenger-friendly way. The numerical simulations of a full-scale rocket-plane were performed using the simulation and dynamic stability analyzer (SDSA) software package. The influence of an elevator deflection change on flight parameters was investigated in two cases: a transition from the steep descent at high angles of attack to the level glide just after rocket-plane release from the carrier and an analogous transition after re-entry to the atmosphere. In particular, G-loads and G-rates were analyzed. Findings As a result, it was found that the values of these parameters satisfied the specific requirements during the separation and transition from a steep descent to gliding. They would be acceptable for an average passenger. Research limitations/implications To verify the modeling approach, a flight test campaign was performed. During the experiment, a rocket-plane scaled model was released from the RC model helicopter. The rocket-plane model was geometrically similar only. Froude scales were not applied because they would cause excessive technical complications. Therefore, a separate simulation of the experiment with the application of the scaled model was performed in the SDSA software package. Results of this simulation appeared to be comparable to flight test results so it can be concluded that results for the full-scale rocket-plane simulation are also realistic. Practical implications It was proven that the rocket-plane in a strake-wing configuration could meet the FAA recommendation concerning G-loads and G rates during suborbital flight. Moreover, it was proven that the SDSA software package could be applied successfully to simulate flight characteristics of airplanes flying at angles of attack not only lower than stall angles but also greater than stall angles. Social implications The application of rocket-planes in a strake-wing configuration could make suborbital tourist flights more popular, thus facilitating the development of manned space flights and contributing to their cost reduction. That is why it was so important to prove that they could meet the FAA recommendation for this kind of service. Originality/value The original design of the rocket plane was analyzed. It is equipped with an optimized strake wing and is controlled with oblique, all moving, wingtip plates. Its post-stall flight characteristics were simulated with the application of the SDSA software package which was previously validated only for angles of attack smaller than stall angle. Therefore, experimental validation was necessary. However, because of excessive technical problems caused by the application of Froude scales it was not possible to perform a conventional test with a dynamically scaled model. Therefore, the geometrically scaled model was built and flight tested. Then a separate simulation of the experiment with the application of this model was performed. Results of this separate simulation were compared with the results of the flight test. This comparison allowed to draw the conclusion on the applicability of the SDSA software for post-stall analyzes and, indirectly, on the applicability of the proposed rocket-plane for tourist suborbital flights. This approach to the experimental verification of numerical simulations is quite unique. Finally, a quite original method of the model launching during flight test experiment was applied.

Identification of a degradation of aerodynamic characteristics of a paraglider due to its flexibility from flight test

2019 ◽  
Vol 91 (6) ◽  
pp. 873-879 ◽  
Author(s):  
Robert Kulhánek
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Leading Edge ◽  
Flight Test ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Content Type ◽  
Specific Geometry ◽  
Lift And Drag ◽  
Scaled Models

Purpose Aerodynamics of paragliders is very complicated aeroelastic phenomena. The purpose of this work is to quantify the amount of aerodynamic drag related to the flexible nature of a paraglider wing. Design/methodology/approach The laboratory testing on scaled models can be very difficult because of problems in the elastic similitude of such a structure. Testing of full-scale models in a large facility with a large full-scale test section is very expensive. The degradation of aerodynamic characteristics is evaluated from flight tests of the paraglider speed polar. All aspects of the identification such as pilot and suspension lines drag and aerodynamics of spanwise chambered wings are discussed. The drag of a pilot in a harness was estimated by means of wind tunnel testing, computational fluid dynamics (CFD) solver was used to estimating smooth wing lift and drag characteristics. Findings The drag related to the flexible nature of the modern paraglider wing is within the range of 4-30 per cent of the total aerodynamic drag depending on the flight speed. From the results, it is evident that considering only the cell opening effect is sufficient at a low-speed flight. The stagnation point moves forwards towards the nose during the high speed flight. This causes more pronounced deformation of the leading edge and thus increased drag. Practical implications This paper deals with a detailed analysis of specific paraglider wing. Although the results are limited to the specific geometry, the findings help in the better understanding of the paraglider aerodynamics generally. Originality/value The data obtained in this paper are not affected by any scaling problems. There are only few experimental results in the field of paragliders on scaled models. Those results were made on simplified models at very low Reynolds number. The aerodynamic drag characteristics of the pilot in the harness with variable angles of incidence and Reynolds numbers have not yet been published.

Deflation of metrizamide-filled balloon used to occlude a carotid-cavernous fistula

1983 ◽  
Vol 59 (3) ◽  
pp. 524-528 ◽  
Author(s):  
Thomas J. Leipzig ◽  
Sean F. Mullan
Keyword(s):  
Contrast Agent ◽  
Vascular Wall ◽  
Carotid Cavernous Fistula ◽  
Technical Problems ◽  
Content Type ◽  
Cavernous Fistula ◽  
Short Summary ◽  
Carotid Cavernous Fistulas ◽  
Fine Print

✓ A carotid-cavernous fistula was occluded by a detachable latex balloon. Because of technical problems, the contrast-filled balloon was left in a precarious position in the ostium of the fistula. Premature deflation of the balloon would have resulted in intra-arterial migration of the device. Approximately 1 week is required for the balloon to become secured in place by fibrous attachment to the vascular wall. For success, if the ligature is adequate, a detachable Debrun balloon should remain inflated for this period of time. The deflation process was monitored radiographically in this patient. The balloon remained inflated for at least 2 weeks. A short summary of the experience with deflation of various contrast-containing balloon devices in the treatment of carotid-cavernous fistulas is given. Metrizamide may be the best contrast agent for use in these devices.

Guidelines for CFD Simulations of Spar VIM

2013 ◽  
Author(s):  
Charles Lefevre ◽  
Yiannis Constantinides ◽  
Jang Whan Kim ◽  
Mike Henneke ◽  
Robert Gordon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Mooring System ◽  
Time Step ◽  
Cfd Simulations ◽  
Scaled Model ◽  
Sway Motion

Vortex-Induced Motion (VIM), which occurs as a consequence of exposure to strong current such as Loop Current eddies in the Gulf of Mexico, is one of the critical factors in the design of the mooring and riser systems for deepwater offshore structures such as Spars and multi-column Deep Draft Floaters (DDFs). The VIM response can have a significant impact on the fatigue life of mooring and riser components. In particular, Steel Catenary Risers (SCRs) suspended from the floater can be sensitive to VIM-induced fatigue at their mudline touchdown points. Industry currently relies on scaled model testing to determine VIM for design. However, scaled model tests are limited in their ability to represent VIM for the full scale structure since they are generally not able to represent the full scale Reynolds number and also cannot fully represent waves effects, nonlinear mooring system behavior or sheared and unsteady currents. The use of Computational Fluid Dynamics (CFD) to simulate VIM can more realistically represent the full scale Reynolds number, waves effects, mooring system, and ocean currents than scaled physical model tests. This paper describes a set of VIM CFD simulations for a Spar hard tank with appurtenances and their comparison against a high quality scaled model test. The test data showed considerable sensitivity to heading angle relative to the incident flow as well as to reduced velocity. The simulated VIM-induced sway motion was compared against the model test data for different reduced velocities (Vm) and Spar headings. Agreement between CFD and model test VIM-induced sway motion was within 9% over the full range of Vm and headings. Use of the Improved Delayed Detached Eddy Simulation (IDDES, Shur et al 2008) turbulence model gives the best agreement with the model test measurements. Guidelines are provided for meshing and time step/solver setting selection.

Experimental study on fire resistance of a full-scale composite floor assembly in a two-story steel framed building

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lisa Choe ◽  
Selvarajah Ramesh ◽  
Xu Dai ◽  
Matthew Hoehler ◽  
Matthew Bundy
Keyword(s):  
Natural Gas ◽  
Fire Resistance ◽  
Full Scale ◽  
System Level ◽  
Compartment Fire ◽  
Content Type ◽  
Standard Fire ◽  
Fire Experiment ◽  
The Usa ◽  
Floor System

PurposeThe purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.Design/methodology/approachThe fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.FindingsAlthough the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm2/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.Originality/valueThis work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.

scholarly journals Fully resolved numerical simulations of fused deposition modeling. Part II – solidification, residual stresses and modeling of the nozzle

2018 ◽  
Vol 24 (6) ◽  
pp. 973-987 ◽  
Author(s):  
Huanxiong Xia ◽  
Jiacai Lu ◽  
Gretar Tryggvason
Keyword(s):  
Residual Stresses ◽  
Numerical Simulations ◽  
Fused Deposition Modeling ◽  
Fixed Bed ◽  
Ground Truth ◽  
Deposition Process ◽  
Material Behavior ◽  
Content Type ◽  
Fused Deposition ◽  
Deposition Modeling

Purpose The purpose of this paper is to continue to describe the development of a comprehensive methodology for fully resolved numerical simulations of fused deposition modeling. Design/methodology/approach A front-tracking/finite volume method introduced in Part I to simulate the heat transfer and fluid dynamics of the deposition of a polymer filament on a fixed bed is extended by adding an improved model for the injection nozzle, including the shrinkage of the polymer as it cools down, and accounting for stresses in the solid. Findings The accuracy and convergence properties of the new method are tested by grid refinement, and the method is shown to produce convergent solutions for the shape of the filament, the temperature distribution, the shrinkage and the solid stresses. Research limitations/implications The method presented in the paper focuses on modeling the fluid flow, the cooling and solidification and volume changes and residual stresses, using a relatively simple viscoelastic constitutive model. More complex material models, depending, for example, on the evolution of the conformation tensor, are not included. Practical implications The ability to carry out fully resolved numerical simulations of the fused deposition process is expected to be critical for the validation of mathematical models for the material behavior, to help explore new deposition strategies and to provide the “ground truth” for the development of reduced-order models. Originality/value The paper completes describing the development of the first numerical method for fully resolved simulation of fused filament modeling.

Ecosystem-based disaster risk reduction concept for forest and land fire disaster

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Philein Hafidz Al Kautsar ◽  
Nur Budi Mulyono
Keyword(s):  
Law Enforcement ◽  
Disaster Management ◽  
Real Life ◽  
Structured Interview ◽  
Technical Problems ◽  
Content Type ◽  
Economic Problems ◽  
Technology And Innovation ◽  
Management Of Technology ◽  
Management Context

PurposeThe purpose of this study is to develop an ecosystem-based DRR concept and explore how far the concept can be applied in a disaster-management context.Design/methodology/approachThe authors used the ecosystem concept established by Tsujimoto et al. (2018) as the foundation of this study. They then conducted a literature search to adapt the ecosystem concept to fit the context of disaster management. Thus, they developed an ecosystem-based DRR concept. They used a case study method to test whether the adapted ecosystem concept can be applied to examine a real-life case of disaster management. For data collection, they used qualitative methods; a semi-structured interview with practitioners and other actors involved in disaster-management practice as well as document review. For data analysis, they used thematic analysis to find themes within the data.FindingsBy using this concept, the authors found some actors fulfil their role in the ecosystem toward the DRR effort, some actors are ill-equipped, and some actors are actively working against DRR effort. There are also implementation challenges, as numerous programs are only halfway done due to a lack of resources. However, the main problems of this disaster can be summarized into three categories: technical problems, socio-economic problems and law-enforcement problems. All three problems need to be addressed altogether because even neglecting only one problem would lead to a flawed solution.Research limitations/implicationsOne of the limitations is the respondents' bias. This research aims to find out their part, or more accurately what they are representative of, regarding disaster management for forest and land fire case. As some of the questions may reveal unflattering action or may even hurting their credibility, respondents might not have provided an entirely honest answer. Another limitation is the differing respondents' roles within the disaster. As each of the respondents is a representative of an actor in disaster management, they all have different traits. Thus, this situation makes it challenging to produce similar quality and quantity data for each of them.Practical implicationsAs concluded, the ecosystem-based DRR concept can be used as a framework to examine a real-life case of disaster management. It can be utilized to explain roles, relationships and the whole network of disaster-management actors. The authors hope that this concept could help decision-makers in designing their policies.Social implicationsThe main problems of this disaster can be summarized into three categories: technical problems, socio-economic problems and law-enforcement problems. All three problems need to be addressed altogether for even neglecting only one problem would lead to a flawed solution. However, the yearly reoccurrences of fires and the widespread of illegal and dangerous practice, slash and burn agriculture, are evidence that the government mishandles the other two problems. There is a need for reform within legal institutions and government's treatment regarding local farmers. There is a need for trust, cooperation and synergy between disaster-management actors.Originality/valueThe ecosystem concept has been used widely in the field of management of technology and innovation. However, while ecosystem concept is commonly used in the management of technology and innovation, it is rarely used in a disaster-management context.

Use of e-learning at higher educational institutions in Bangladesh

2019 ◽  
Vol 11 (2) ◽  
pp. 210-223 ◽  
Author(s):  
Md Fouad Hossain Sarker ◽  
Rafi Al Mahmud ◽  
M. Saiful Islam ◽  
Md Kabirul Islam
Keyword(s):  
Learning Technologies ◽  
Primary Data ◽  
Educational Institutions ◽  
Higher Educational Institutions ◽  
Technical Problems ◽  
Content Type ◽  
Learning Platform ◽  
E Learning ◽  
Learning Platforms ◽  
Higher Educational

Purpose Although e-learning has already been accepted globally as an effective medium of delivery of quality education and ensure optimum student participation, Bangladeshi higher educational institutions are still at a very early stage of adopting such technologies. Therefore, the purpose of this paper is to critically examine the suitability of implementing effective e-learning through learning management system (LMS) at the tertiary educational institutions in Bangladesh, and how both students and teachers experience and respond to this new learning platform. Following mixed-methods techniques, data for this study were collected from students and respective course teachers of a private university in Bangladesh by administering questionnaires and in-depth interviews. The findings of this paper reveal that e-learning has been well accepted by most of the students as they are found routinely spending time on the LMS on a regular basis for watching lecture videos, viewing course information, reading postings of the fellow students in the forum. However, there are constraints as well, since the learning materials are poorly designed that do not allow much interaction between students and lecturers. There are also some technical problems such as poor internet connection which restrict access to e-learning platforms. To harness the optimum benefit of e-learning, this paper recommends a concerted effort by all stakeholders, such as students, lecturers, administrators and policy makers so that each of their priorities and expectations are reflected in the designing and implementing e-learning platforms. Design/methodology/approach This paper is based on the qualitative evaluation of Education 3.0 platform. Primary data were collected from the students using a well-structured survey questionnaire, and the findings of the survey have subsequently been cross-referred and supplemented by non-participatory observations with semi-structured interviews which allowed a better in-depth understanding of the issue at hand. Findings The findings of the study suggest that a majority of the students are found to be highly enthusiastic about the online courses. They are eager to participate and interact in the online platforms, which are somehow limited in the traditional classroom settings. However, there are several institutional, administrative and technical limitations of implementing e-learning in Bangladesh. It is recommended that better orientation of the users, quality content distribution though user-friendly systems and enhanced asynchronous interaction between the lecturers and students are the key pre-requisites to harness the optimum benefit from e-learning technologies in Bangladesh. Originality/value The data have been analyzed and discussed using qualitative framework which allows an in-depth understanding of the opportunities and challenges of the use of e-learning technologies at the higher educational institutions in Bangladesh.

Experimental investigation on wheel–rail adhesion characteristics under water and large sliding conditions

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Jiajun Zhou ◽  
Mengling Wu ◽  
Chun Tian ◽  
Zewang Yuan ◽  
Chao Chen
Keyword(s):  
Peer Review ◽  
Theoretical Description ◽  
Full Scale ◽  
Theoretical Research ◽  
Slip Ratio ◽  
Content Type ◽  
Adhesion Coefficient ◽  
Experimental Base ◽  
New Ideas ◽  
Roller Rig

Purpose The purpose of this study is to investigate the adhesion characteristics of the wheel–rail under water and large sliding conditions. This is carried out by conducting a series of tests on a full-scale roller rig. The measured data provides an experimental base for conducting further theoretical research. Design/methodology/approach The influence of the slip ratio, rolling speed and the axle load on the adhesion coefficient between the wheel and the rail is analyzed under wet conditions using a full-scale roller rig. Findings From the research, it is found that the adhesion coefficient–slip ratio curve varies from the traditional theoretical description under water and large sliding conditions. Moreover, it is also observed that after the adhesion coefficient reaches the saturation point, the adhesion coefficient does not decrease, but continues to increase as the slip ratio increases. Originality/value The adhesion improvement phenomenon in this paper may provide new ideas for designing anti-skid control and braking system mechanisms for trains. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0236/

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