Space–time FSI modeling and dynamical analysis of spacecraft parachutes and parachute clusters

Computer modeling of spacecraft parachutes, which are quite often used in clusters of two or three large parachutes, involves fluid–structure interaction (FSI) between the parachute canopy and the air, geometric complexities created by the construction of the parachute from “rings” and “sails” with hundreds of gaps and slits, and the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T \bigstar AFSM){({{\rm T} \bigstar {\rm AFSM}})} has successfully addressed the computational challenges related to the FSI and geometric complexities, and recently started addressing the challenges related to the contact between the parachutes of a cluster. The core numerical technology is the stabilized space–time FSI technique developed and improved over the years by the T \bigstar AFSM{{{\rm T} \bigstar {\rm AFSM}}} . The special technique used in dealing with the geometric complexities is the Homogenized Modeling of Geometric Porosity, which was also developed and improved in recent years by the T \bigstar AFSM{{{\rm T} \bigstar {\rm AFSM}}} . In this paper we describe the technique developed by the T \bigstar AFSM{{{\rm T} \bigstar {\rm AFSM}}} for modeling, in the context of an FSI problem, the contact between two structural surfaces. We show how we use this technique in dealing with the contact between parachutes. We present the results obtained with the FSI computation of parachute clusters, the related dynamical analysis, and a special decomposition technique for parachute descent speed to make that analysis more informative. We also present a special technique for extracting from a parachute FSI computation model parameters, such as added mass, that can be used in fast, approximate engineering analysis models for parachute dynamics.     

Detection and tracking of sea-surface targets in infrared and visual band videos using the bag-of-features technique with scale-invariant feature transform

Sea-surface targets are automatically detected and tracked using the bag-of-features (BOF) technique with the scale-invariant feature transform (SIFT) in infrared (IR) and visual (VIS) band videos. Features corresponding to the sea-surface targets and background are first clustered using a training set offline, and these features are then used for online target detection using the BOF technique. The features corresponding to the targets are matched to those in the subsequent frame for target tracking purposes with a set of heuristic rules. Tracking performance is compared with an optical-flow-based method with respect to the ground truth target positions for different real IR and VIS band videos and synthetic IR videos. Scenarios are composed of videos recorded/generated at different times of day, containing single and multiple targets located at different ranges and orientations. The experimental results show that sea-surface targets can be detected and tracked with plausible accuracies by using the BOF technique with the SIFT in both IR and VIS band videos.     

泰克煤炭公司炼焦煤煤质及炼焦性能的研究

对加拿大泰克煤炭公司5个单种煤样进行煤质分析,并分别用40kg、200kg和400kg试验焦炉进行炼焦试验。5个单种煤的灰、硫较低,黏结性较好,除TCA煤是简单混煤外,其余均为单一煤层煤,属于较好的炼焦煤类。5个试验煤样随着煤变质程度由高到低所得试验焦炭冷强度和热性质也由高到低;200kg和400kg试验焦炉所得焦炭的冷热态强度综合排列趋势基本一致,并与加拿大第三方实验室炼焦数据趋势基本一致,而40kg试验焦炉所得焦炭的排列趋势却与之差异明显。     

Effect of dust content on some properties of concrete

Natural aggregates with three different gradings have been used to produce concretes with a constant water cement ratio of 0.5 and cement contents varying between 300 kg/m³ and 425 kg/m³. Aggregate gradings differed only in the dust (particles smaller than 300 μm) contents: Nil, 3%, 9%. Dust deficient aggregates always produced less workable concretes for cement contents below 330 kg/m³. These concretes were also less strong than the others. As a result for this particular case, minimum cement content of 330 kg/m³ is recomended for concretes produced with dust deficient aggregates, instead of the common minimum of 300 kg/m³. Additional cement seems to compensate for the missing dust in the mixes tried.     

A PRACTICAL APPROACH FOR FIELD SCALE PERFORMANCE ESTIMATION OF WATER INJECTION IN FRACTURED OIL RESERVOIRS

In this study, a practical method is developed to predict the waterflooding performance in naturally fractured reservoirs (NFR) if the production rate is dominated by the capillary imbibition transfer between matrix and fracture. Capillary imbibition transfer rate is defined explicitly as a function of matrix (permeability, wettability, and size), flow (rate or velocity) and reservoir (size) properties. Verification of the formulation is based on previously performed experimental and numerical studies. Then, a correlation between total water injected and total oil produced is developed using the abstract relationship between recovery and time proposed by Aranofsky et al. (1958). A parametric study is performed to obtain a critical (or optimum) injection rate for an efficient recovery of oil. It is shown that a critical injection rate value exists depending on the capillary suction capability of matrix. Beyond the critical rate, the process becomes inefficient as the increasing rate would not yield a faster oil recovery.