阻力方程n^（3／2）X＝n_b^（3／2）X_b＋n_w^（3／2）X_w在数学领域内的合理性

本文将数学中解的存在条件和河流动力学的基本原理相结合，从另一个角度导出了爱因斯坦处理河道横断面综合阻力与河床、河岸阻力之间的关系，为该公式的合理性提供了数学领域内的证明．

粘性泥石流阻力和运动方程验证分析

现有的粘性泥石流阻力运动方程可以大致归纳为三类：一类是将泥石流视为固液两相流，通过理论分析建立的泥石流阻力运动方程；二类是认为粘性泥石流符合宾汉姆流体阻力方程；三类是依据泥石流体具有基本符合库伦公式的剪切强度，将泥石流视为固体颗粒散体重力流，在理论分析基础上建立的阻力和运动方程。用粘性泥石流动力学实验数据对三类阻力运动方程进行了验证，结果表明第三类阻力和运动方程与实际接近。

基于盖帽模型的混凝土动态球型空腔膨胀模型和侵彻阻力分析

为了获得弹丸高速侵彻混凝土介质的阻力方程,提出了一种基于混凝土盖帽模型的球形动态空腔膨胀模型。利用一般形式的状态方程和屈服准则描述混凝土材料的动态力学特性,获得了通用混凝土球形空腔膨胀模型的动态响应表达式。通过引入Dracker-Prager Cap屈服模型,在新的空腔膨胀模型中考虑了混凝土高压下的屈服软化特性。计算结果表明:采用带剪切饱和的Mohr-Coulomb屈服准则与Tresca屈服准则推导出的阻力方程在高速阶段与盖帽模型差别较大。实验结果证明:基于盖帽模型的球形空腔膨胀模型因考虑混凝土高压屈服软化特性与实验结果具有更好的一致性。

浆体管道输送中两种阻力损失计算方法的分析

根据现场系统的实测数据和理论计算结果的比较，分析和评价了浆体管道输送中两种阻力损失的计算方法，编制了Ｗａｓｐ 法的计算程序。

耐高矿化度超支化聚合物滑溜水压裂液减阻与流变性关系研究

滑溜水压裂液是页岩气等非常规油气藏开采的重要材料,为明确高矿化度下聚合物滑溜水压裂液流变性与减阻性能关系,研究了超支化聚合物在不同浓度和不同矿化度下的流变性能,同时在大型摩擦阻力测试装置中测试其压差数据和摩擦阻力性能,在20万矿化度下减阻率可以达到70%左右。分析了聚合物的浓度、高矿化度对超支化聚合物流变性与减阻率的影响。并将计算得到的超支化聚合物在管路中流动的摩擦阻力系数(f)、广义雷诺数(Re)与聚合物溶液流变学参数(n)相关联,建立了表征高矿化度条件下超支化聚合物溶液摩擦阻力系数新方程,并获得了高矿化度下滑溜水摩阻系数与Re的幂律关系式。

非光滑管路中HPAM溶液减阻与流变性关系研究

通过研究不同分子量、不同浓度的部分水解聚丙烯酰胺(HPAM)溶液的流变性能,并测试其在大型摩擦阻力测试装置中的压差,探究聚合物浓度、聚合物分子量等因素对HPAM溶液在非光滑管路中减阻性能的影响。结果表明,在实验条件范围内,聚合物分子量增大,溶液的减阻率先降低后升高;聚合物的浓度增大,溶液的减阻率降低。通过计算得到了HPAM溶液在内径为0.46 cm非光滑管路中流动时的摩擦阻力系数f和广义雷诺数Re并与HPAM溶液流型参数n相关联,建立了表征非光滑管路中聚合物溶液摩擦阻力系数新方程,同时建立了聚合物溶液摩擦阻力系数f与广义雷诺数Re、减阻率DR与广义雷诺数Re的经验关系,便于HPAM溶液的工程应用。

Indentation size effect of germanium single crystal with different crystal orientations

In order to study the indentation size effect(ISE)of germanium single crystals,nano-indentation experiments were carried out on the(100),(110)and(111)plane-orientated germanium single crystals.The true hardness of each crystal plane of germanium single crystals was calculated based on the Meyer equation,proportional sample resistance(PSR)model and Nix-Gao model,and the indentation size effect(ISE)factor of each crystal plane was calculated.Results show that,the germanium single crystals experience elastic deformation,plastic deformation and brittle fracture during the loading process,and the three crystal planes all show obvious ISE phenomenon.All three models can effectively describe the ISE of germanium single crystals,and the calculated value of Nix-Gao model is the most accurate.Compared with the other two crystal planes,Ge(110)has the highest size effect factor m and the highest hardness,which indicates that Ge(110)has the worst plasticity.

Control of Vortex Shedding and Drag Reduction through Dual Splitter Plates Attached to a Square Cylinder

In this paper we have made a numerical study on the control of vortex shedding and drag reduction of a cylinder by attaching thin splitter plates. The wake structure of the cylinder of square cross-section with attached splitter plates is analyzed for a range of Reynolds number, based on the incident stream and height of the cylinder, in the laminar range. The Navier-Stokes equations governing the flow are solved by the control volume method over a staggered grid arrangement. We have used the semi-implicit method for pressure-linked equation （SIMPLE） algorithm for computation. Our results show that the presence of a splitter plate upstream of the cylinder reduces the drag, but it has a small impact on the vortex shedding frequency when the plate length is beyond 1.5 time the height of the cylinder. The presence of a downstream splitter plate dampens the vortex shedding frequency. The entrainment of fluid into the inner side of the separated shear layers is obstructed by the downstream splitter plate. Our results suggest that by attaching in-line splitter plates both upstream and downstream of the cylinder, the vortex shedding can be suppressed, as well as a reduction in drag be obtained. We made a parametric study to determine the optimal length of these splitter plates so as to achieve low drag and low vortex shedding frequency.

Aerodynamic drag analysis of double-deck container vehicles with different structures

To study the aerodynamic performance of a new six-axis X2K double-deck container vehicle, numerical simulation was done based on three-dimensional, steady Navier-Stokes equations and k-e turbulence model. The results show that the pressure on the front surface of vehicle is positive, and others are negative. The maximum negative one appears as a ＂gate＂ shape on front surfaces. The pressure on vehicle increases with train speed, and pressure on vehicles with cross-loaded structure is smaller than that without it. The airflow around vehicles is symmetrical about train vertical axis, and the flow velocity decreases gradually along the axis to ground. Airflow around vehicles with cross-loaded structure is weaker than that without the structure. The aerodynamic drag increases linearly with the train speed, and it is minimum for the mid-vehicle. The linear coefficient for mid-vehicle without cross-loaded structure is 29.75, nearly one time larger than that with the structure valued as 15.425. So, from the view-point of aerodynamic drag, the cross-loaded structure is more reasonable for the six-axis X2K double-deck container vehicle.

Kamenev-type criteria for nonlinear damped dynamic equations

We establish a new Kamenev-type theorem for a class of second-order nonlinear damped delay dynamic equations on a time scale by using the generalized Riccati transformation technique. The criterion obtained improves related contributions to the subject. An example is provided to illustrate assumptions in our theorem are less restrictive.

One neural network approach for the surrogate turbulence model in transonic flows

With the rapid development of artificial intelligence techniques such as neural networks,data-driven machine learning methods are popular in improving and constructing turbulence models.For high Reynolds number turbulence in aerodynamics,our previous work built a data-driven model applicable to subsonic airfoil flows with different free stream conditions.The results calculated by the proposed model are encouraging.In this work,we aim to model the turbulence of transonic wing flows with fully connected deep neural networks,where there is less research at present.The proposed model is driven by two flow cases of the ONERA(Office National d'Etudes et de Recherches Aerospatiales)wing and coupled with the Navier-Stokes equation solver.Four subcritical and transonic benchmark cases of different wings are used to evaluate the model performance.The iteration process is stable,and final convergence is achieved.The proposed model can be used to surrogate the traditional Reynolds averaged Navier-Stokes turbulence model.Compared with the data calculated by the Spallart-Allmaras model,the results show that the proposed model can be well generalized to the test cases.The mean relative error of the drag coefficient at different sections is below 4%for each case.This work demonstrates that modeling turbulence by data-driven methods is feasible and that our modeling pattern is effective.

Review:J-integral resistance curve testing and evaluation

In this paper a critical review is presented of the history and current state of the art of J-integral resistance curve testing and experimental evaluation methods in conjunction with a discussion of the development of the plane strain fracture toughness test standard ASTM E1820 developed by American Society for Testing and Materials (ASTM). Early research efforts on this topic are reviewed first. These include the J-integral concept, experimental estimates of the J-integral for stationary cracks, load line displacement (LLD) and crack mouth opening displacement (CMOD) based η factor equations, different formulations of J-integral incremental equations for growing cracks, crack growth corrected J-R curve determination, and experimental test methods. Recent developments in J-R curve testing and evaluation are then described, with emphasis on accurate J-integral incremental equations, a normalization method, a modified basic method, a CMOD direct method with use of incremental equations, relationships of plastic geometry factors, constraint-dependent J-R curve testing and correction approaches. An overview of the present fracture toughness test standard ASTM E1820-08a is then presented. The review shows that after more than 40 years of investigation and development, the J-integral resistance curve test methods in ASTM E1820 have become simpler, more cost-effective and more accurate.