阅读说明：本技术 一种低强度和高强度流动结构融合显示方法 (Fusion display method for low-strength and high-strength flow structures ) 是由 刘俊 胡皓博 王萍 蓝嘉晖 杨虹 于 2021-09-14 设计创作，主要内容包括：本发明涉及一种低强度和高强度流动结构融合显示方法,其特征在于,包括：修改数值水气比拟中的光照强度计算公式为其中β为可调参数,为密度梯度,为全场密度梯度的最大值,σ(s)为光照强度,k(k>0)为调节参数；设定参数β和k,使得绘制的低强度流动结构和高强度流动结构满足亮度差和背景亮度两方面的要求。实施本发明一种低强度和高强度流动结构融合显示方法,在数值水气比拟可视化方法的基础上,通过发展一种能够适应不同强度流场结构显示的光照模型,有效解决高强度流动结构和低强度流动结构难以融合显示的问题,为揭示流动结构之间的内在联系提供一种新的可视化工具。(The invention relates to a fusion display method for low-strength and high-strength flow structures, which is characterized by comprising the following steps: modifying the formula for calculating the illumination intensity in numerical water-gas ratio Is composed of Wherein beta is an adjustable parameter, and beta is an adjustable parameter, in order to be a density gradient, the density gradient, maximum of the full field density gradient, σ(s) is the illumination intensity, k (k)>0) To adjust the parameters; parameters beta and k are set so that the drawn low-intensity flow structure and high-intensity flow structure meet the requirements of both brightness difference and background brightness. By implementing the fusion display method for the low-strength and high-strength flow structures, the problem that the high-strength flow structures and the low-strength flow structures are difficult to fuse and display is effectively solved by developing an illumination model which can adapt to the display of the flow structures with different strengths on the basis of a numerical water-gas ratio visualization method, and a new visualization tool is provided for revealing the internal relation between the flow structures.)

1. A low-intensity and high-intensity flow structure fusion display method is characterized by comprising the following steps:

modifying the formula for calculating the illumination intensity in numerical water-gas ratioIs composed of Wherein beta is an adjustable parameter, and beta is an adjustable parameter, in order to be a density gradient, the density gradient,maximum of the full field density gradient, σ(s) is the illumination intensity, k (k)>0) To adjust the parameters;

parameters beta and k are set so that the drawn low-intensity flow structure and high-intensity flow structure meet the requirements of both brightness difference and background brightness.

2. The method of claim 1, wherein the low intensity flow structure comprises an acoustic wave, a weak compressional wave, a numerical pseudo wave in a flow field.

3. The low intensity and high intensity flow structure fusion display method of claim 1 wherein the high intensity flow structure comprises shock waves, large scale vortices in a flow field.

4. The method for fusion display of low-intensity and high-intensity flow structures according to any one of claims 1 to 3, wherein the low-intensity flow structure corresponds to a dimensionless density gradient s₁，s₁Of the order of 10^-4The following.

5. The method of claim 4, wherein the difference between the illumination intensity of the low-intensity flow structure and the illumination intensity of the uniform area of the flow field is at least σ₁Namely:

6. the method for fusion display of low-intensity and high-intensity flow structures according to claim 5, wherein the high-intensity flow structure corresponds to a dimensionless density gradient s₂，s₂Of the order of 10^-1～10^-2。

7. The method of claim 6, wherein the high-intensity flow structure background luminance is at least σ₂Namely:

8. the low-intensity and high-intensity flow structure fusion display method according to claim 7, wherein combining equations (3) and (4) yields:

wherein, the calculation formula of beta and k comprises four variables sigma₁、σ₂、s₁And s₂。σ₁And σ₂Is a constant, σ₁The value is 0.04-0.06, sigma₂The value is 0.2-0.4, s₁And s₂The adjustment is made according to the strength of the low-strength and high-strength flow structures.

Technical Field

The invention relates to the technical field of flow field display, in particular to a fusion display method for low-strength and high-strength flow structures.

Background

To reveal the interaction between flow structures, fused representations of different types of flow structures of different strengths are required. Zhou et al (2012) extracted three-dimensional vortices and small shock waves by using a Q criterion and an expansion isosurface method respectively, and fused and displayed the three-dimensional vortices and the small shock waves to reveal the generation mechanism of the small shock waves. Pirozzoli et al (2011) extracts a shock wave surface by using Ducros shock wave detection factors, extracts a vortex structure in a boundary layer by using a lambda2 method, and fuses the two to present a shock wave/boundary layer interference flow field. Despite advances in the fusion visualization of partial flow structures, deficiencies in methods and techniques are still encountered. The density gradient gray scale map used by Dauptain et al plots the supersonic jet-plate collision flow field. They found that when the density gradient display interval is large, only structures such as shock waves and large-scale vortices exist in the flow field, and as the density gradient display interval is gradually reduced, small-scale structures and sound waves in the flow field begin to appear, but the shock waves and the large-scale structures become fuzzy. For this reason, they have drawn three pictures to present most of the flow structure information in the flow field by changing the density gradient display interval. Huang and the like draw shock wave buffeting flow fields based on density gradients and swelling capacity, and analysis shows that the density gradient gray-scale map can clearly distinguish shock waves and large-scale vortexes, and the swelling capacity gray-scale map has a good display effect on sound waves. Christoph and the like draw a flow field of the collision of the supersonic jet and the inclined plate by adopting a passive scalar, a Q-criterion isosurface and an expansion amount respectively. The passive scalar has a good display effect on the shear layer multi-scale vortex, the Q criterion has a good display effect on the radiation sound wave, and the expansion amount well represents the shock wave in the impact area.

Currently, in the aspect of flow structure fusion display, a main problem is that it is difficult to realize fusion display of a high-strength structure (specifically, a flow structure with a large density gradient, including shock waves, large-scale vortices and the like) and a low-strength structure (specifically, a flow structure with a small density gradient, including sound waves, small-scale vortices and the like) in a flow field. When the flow structure is visualized, the main flow structure in the flow field can be presented by drawing a plurality of pictures by combining a plurality of display methods or by adjusting display parameters. The multi-picture display of the flow structure can cause the correlation among different flow structures to be difficult to find, and forces researchers to spend a great deal of time and energy for the comparison among different pictures, thereby severely restricting the research and development efficiency.

Thus, significant advances in the art are needed.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a fusion display method for low-intensity and high-intensity flow structures, which includes:

modifying the formula for calculating the illumination intensity in numerical water-gas ratioIs composed of Wherein beta is an adjustable parameter, and beta is an adjustable parameter, in order to be a density gradient, the density gradient,maximum of the full field density gradient, σ(s) is the illumination intensity, k (k)>0) To adjust the parameters;

parameters beta and k are set so that the drawn low-intensity flow structure and high-intensity flow structure meet the requirements of both brightness difference and background brightness.

Preferably, the low intensity flow structure comprises acoustic waves, weak compressional waves, numerical pseudo waves in the flow field.

Preferably, the high intensity flow structure comprises shock waves, large scale vortices in the flow field.

Preferably, the low-intensity flow structure corresponds to a dimensionless density gradient of s₁，s₁Of the order of 10^-4The following.

Preferably, the difference between the illumination intensity of the low-intensity flow structure and the illumination intensity of the uniform area of the flow field is at least sigma₁Namely:

preferably, the high-strength flow structure corresponds to a dimensionless density gradient of s₂，s₂Of the order of 10^-1～10^-2。

Preferably, the high intensity flow structure background luminance is at least σ₂Namely:

preferably, combining formula (3) and formula (4) yields:

wherein, the calculation formula of beta and k comprises four variables sigma₁、σ₂、s₁And s₂。σ₁And σ₂Is a constant, σ₁The value is 0.04-0.06, sigma₂The value is 0.2-0.4, s₁And s₂The adjustment is made according to the strength of the low-strength and high-strength flow structures.

The low-strength and high-strength flow structure fusion display method has the following beneficial effects: on the basis of a numerical value water-gas comparison visualization method, by developing an illumination model capable of adapting to display of flow field structures with different intensities, the problem that a high-intensity flow structure and a low-intensity flow structure are difficult to fuse and display is effectively solved, and a new visualization tool is provided for revealing the internal relation between the flow structures.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a flow chart of a fusion display method of low-strength and high-strength flow structures according to the present invention;

FIG. 2 shows that when β is 10²An effect graph drawn by a numerical water-gas comparison method;

FIG. 3 shows that when β is 10⁴An effect graph drawn by a numerical water-gas comparison method;

FIG. 4 shows that when β is 10⁶An effect graph drawn by a numerical water-gas comparison method;

FIG. 5 shows that when β is 10⁸An effect graph drawn by a numerical water-gas comparison method;

FIG. 6 is a diagram of the effect of the interaction display of the shock wave and the vortex based on the fusion display method of the low-strength and high-strength flow structures of the present invention;

fig. 7 shows β 10²A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method;

fig. 8 shows β 10⁴A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method;

fig. 9 shows β 10⁶A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method;

fig. 10 shows β 10⁸A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method;

fig. 11 is a diagram of the display effect of the double mach-zehnder interferometer based on the fusion display method of the low-intensity and high-intensity flow structure of the present invention.

In the figure, 1-weak compressional wave, 2-shock wave, 3-slip line, 4-vortex, 5-sonic wave.

Detailed Description

The flow field means that the velocity, the pressure and the like all change in one flow field. In the case of flight, caused by the motion of the aircraft; in the wind tunnel experiment, the model is put in the uniform linear airflow, and the model disturbs the airflow. The general term of the flow velocity field, the pressure field and the like defined by the flow velocity, the pressure and other functions of the fluid particle motion described by the Euler method on the time and space point coordinate fields is the spatial distribution of the airflow motion at a certain moment. The information fusion display is a visualization technology capable of presenting different sources and different types of information at the same time. The fusion display of the information of the same type is beneficial to developing comparative analysis among the information, searching reliable information with high consistency and providing more credible data input for decision makers. The fusion display of different types of information is beneficial to improving the information density and more clearly presenting the association relation among various types of information.

Example one

Referring to fig. 1, a flow chart of a method for displaying fusion of low-intensity and high-intensity flow structures according to the present invention is shown. As shown in fig. 1, the method for displaying fusion of low-intensity and high-intensity flow structures according to the first embodiment of the present invention at least includes the following steps:

s1, modifying the numerical water vaporIllumination intensity calculation formula in analogyIs composed ofWherein beta is an adjustable parameter, and beta is an adjustable parameter, in order to be a density gradient, the density gradient,maximum of the full field density gradient, σ(s) is the illumination intensity, k (k)>0) To adjust the parameters;

human eyes are mainly affected by two factors when sensing external objects through brightness. The first major contributor is the luminance difference between the target and the background. When the flow field is drawn, the flow structure can be recognized by human eyes only when the brightness of the flow structure is different from that of the background flow field. The second major influencing factor is the background brightness. The resolving power of human eyes to brightness is inversely proportional to brightness. In the low luminance region, the difference in luminance becomes extremely difficult to distinguish. Therefore, from the principle of human visual perception, the illumination model adopted by the numerical water-air comparison method is improved so as to meet the requirement of fusion display of low-intensity and high-intensity flow structures. In contrast to the original formula (1), the exponent of the variable s becomes the manipulated variable k (k > 0). Equations (1) and (2) have similar mathematical properties.

S2, setting parameters beta and k, so that the drawn low-intensity flow structure and high-intensity flow structure meet the requirements of both brightness difference and background brightness.

Generally, the low-intensity flow structure of interest generally refers to acoustic waves, weak compression waves, numerical artifacts, etc. in the flow field, while the high-intensity flow structure generally refers to shock waves, large-scale vortices, etc. in the flow field. If the intensity of the spatial fluctuation of the flow structure is characterized by the density gradient, the difference between the high-intensity flow structure and the low-intensity flow structure can reach more than 4 magnitude orders.

Assuming a typical low-intensity flow structure corresponding to a dimensionless density gradient of s₁。s₁Is typically of the order of 10^-4The following. The low intensity flow structures are distributed at each corner of the flow field. When low-intensity flow structures and high-intensity flow structures are brought together, the low-intensity structures tend to be difficult to identify because the energy difference is too large. Whereas low-intensity structures that are expected to be identifiable are generally distributed in a uniform area away from high-intensity flow structures. Because the dimensionless density gradient of the uniform area is close to 0, the corresponding brightness is high, and the requirement of human eyes on the background brightness can be met. In order to make the low-intensity structures prominent in the homogeneous region of the flow field, the difference in illumination intensity between the microstructure and the homogeneous region is required to be at least σ₁Namely:

assuming a typical high-intensity flow structure corresponding to a dimensionless density gradient of s₂。s₂Typically on the order of 0.1 or so. The high-strength flow structure has the characteristics of large average density gradient value and large variation amplitude. Due to the fact that the density gradient difference of the high-strength structure is large, the corresponding brightness difference is often large, and the requirement of human eyes on the brightness difference can be met. Whereas in the background brightness, due to s₂The larger the background brightness, the lower the background brightness of the area where the high-intensity flow structure is located, and it is possible to influence the human eye to recognize the target.

For this reason, for high intensity flow structures, a background brightness of at least σ is required₂Namely:

combining formula (3) and formula (4), obtaining:

wherein, the calculation formula of beta and k comprises four variables, wherein sigma₁And σ₂Being constant, the patent proposes σ₁The value is 0.05, sigma₂The value is 0.3. Thus, the parameters β and k are only related to s₁And s₂In this connection, it can be adjusted appropriately according to the strength of the flow structure of interest for the study.

Through the design of the above embodiment, the invention has the beneficial effects that: on the basis of a numerical value water-gas comparison visualization method, by developing an illumination model capable of adapting to display of flow field structures with different intensities, the problem that a high-intensity flow structure and a low-intensity flow structure are difficult to fuse and display is effectively solved, and a new visualization tool is provided for revealing the internal relation between the flow structures.

Example two

By taking two flows of shock wave vortex interaction and double Mach reflection as examples, the display effects of a numerical water-gas ratio method and the low-strength and high-strength flow structure fusion display method are analyzed through comparison.

The interaction between the shock wave and the vortex is a common supersonic flow phenomenon. Taking a certain moment of the interaction of the shock waves and the vortices as an example, a numerical water-gas comparison method and the fusion display method are respectively adopted to draw a flow field.

FIG. 2 shows that when β is 10²An effect graph drawn by a numerical water-gas comparison method; FIG. 3 shows that when β is 10⁴An effect graph drawn by a numerical water-gas comparison method; FIG. 4 shows that when β is 10⁶An effect graph drawn by a numerical water-gas comparison method; FIG. 5 shows that when β is 10⁸And (5) an effect diagram drawn by a numerical water-gas comparison method. As shown in fig. 2-5, when β is 10²The action of the shock waves and vortices inside the vortex can be clearly shown, but the weak compression waves outside the vortex are not evident. If the parameter β is further increased, the weak compressional waves outside the vortex become clearer, but the internal region of the vortex becomes darker significantly, making it difficult to distinguish the internal structure.

FIG. 6 is a diagram of the effect of the interaction display of the shock wave and the vortex based on the fusion display method of the low-strength and high-strength flow structures. As shown in FIG. 6, the low-intensity and high-intensity flow structure fusion display method of the invention is adopted, and the setting parameter is s₁＝10^-5，s₂＝10^-1The effect graph shown in fig. 6 is obtained. As can be seen from FIG. 6, the low-strength and high-strength flow structure fusion display method overcomes the defects of the original method, can clearly display the main flow structure inside the strong vortex, and can better present the weak compression wave outside the vortex.

Through the design of the above embodiment, the invention has the beneficial effects that: on the basis of a numerical value water-gas comparison visualization method, by developing an illumination model capable of adapting to display of flow field structures with different intensities, the problem that a high-intensity flow structure and a low-intensity flow structure are difficult to fuse and display is effectively solved, and a new visualization tool is provided for revealing the internal relation between the flow structures.

EXAMPLE III

The double Mach reflection phenomenon is a special flow phenomenon generated by oblique shock wave incident to an object plane. The double Mach reflection flow contains different types and different strength flow structures such as shock waves, slip lines, vortexes, sound waves and the like. The flow field is drawn by adopting a numerical water-gas comparison method and the fusion display method of the patent respectively.

Fig. 7 shows β 10²A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method; fig. 8 shows β 10⁴A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method; fig. 9 shows β 10⁶A double Mach reflection display effect diagram displayed by a time-value water-gas comparison method; fig. 10 shows β 10⁸The double Mach reflection display effect diagram displayed by the time-value water-gas ratio method. As shown in fig. 7-10, when β is 10²In the process, main flow structures such as shock waves, large-scale vortexes, slip lines and the like can be clearly observed. As β increases, the sound waves in the homogeneous region become clearer, but the large scale vortices become more and more blurred and even difficult to resolve. In general, forIn the numerical water-gas comparison method, small beta value can cause the disappearance of fine flow structures with low intensity, such as sound waves, and the like, and large beta value can cause the difficulty in distinguishing main flow structures, such as large-scale vortexes, and the like.

Fig. 11 is a diagram of the display effect of the double mach-zehnder interferometer based on the fusion display method of the low-intensity and high-intensity flow structure of the present invention. As shown in fig. 11, it can be seen that the low-intensity and high-intensity flow structure fusion display method of the present invention overcomes the defects of the numerical value water-gas comparison method, and can clearly capture fine structures such as sound waves in the uniform region, and simultaneously ensure that the main flow structure has better resolution.

Through the design of the above embodiment, the invention has the beneficial effects that: on the basis of a numerical value water-gas comparison visualization method, by developing an illumination model capable of adapting to display of flow field structures with different intensities, the problem that a high-intensity flow structure and a low-intensity flow structure are difficult to fuse and display is effectively solved, and a new visualization tool is provided for revealing the internal relation between the flow structures.

While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.