## 1 Introduction
Its solid suspension characteristics were studied with the help of computational fluid dynamics (CFDs). The just-suspension speed of the impeller was predicted on the basis of the Eulerian-Eulerian method and modified Brucato drag model. The results showed that the coaxial mixer operating under co-rotation mode should have the best performance, and a faster anchor speed was beneficial to the solid suspension, enhancing the turbulent intensity at the bottom. At the same time, the inner Rushton turbine played a dominant role in the solid suspension due to its high rotational speed. However, an extremely high inner impeller speed would worsen the uniformity of solid distributions. Moreover, the results revealed that a higher overall solid volume fraction and a smaller Shields number worsened the performance of the solid suspension. Moreover, the solid suspension was more susceptible to solid density compared with particle diameter at the same Shields number gradient. The authors of [11] discussed the performance of three different static mixers in terms of pressure drop generated by both single-phase flow and liquid-liquid flow in a turbulent flow regime and in terms of emulsification performance. The three motionless mixers compared were the well-knownSMX(tm) and SMV(tm) and the new version of SMX called SMXPlus(tm). This experimental study aimed at highlighting the influence of dispersed phase concentration and some geometrical parameters such as the number of elements and the design of the motionless mixer on droplet size distribution characteristics. Lastly, experimental results were correlated in terms of Sauter mean diameter as a function of hydrodynamic dimensionless numbers. The authors of [12] compared the performance of the new mixer with the Kenics, SMX, and Komax static mixers. The pressure drop ratio (\(Z\)-factor), coefficient of variation (\(CoV\)), and extensional efficiency (\(\alpha\)) were used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The new mixer showed a superior mixing performance compared to the other mixers. The authors of [13] described the twin-screw conical mixer widely used in industries for its high mixing rate and quality. The effects of rotation speed and sweeping speed on mixing rate and quality were studied. In order to reveal the mixing performance of this mixer, the particle size ratio was investigated. The simulation results indicated that particles were well mixed in the overall and local mixing domain, as well as in the binary system, with a large particle diameter ratio of 1:3. The mixer improved mixing performance at a specific rotation ratio. By considering both the mixing performance and the power consumption, the optimal condition for operation was obtained. Compared with other parts of the mixer, the wear rate on the screw edge was faster [13]. The terms mixers and agitators are often used interchangeably. Mixers are devices that blend combinations of liquids and solids into a homogeneous product. Agitators provide a mechanical action to keep dissolved or suspended solids in solution. Both operate on basically the same principles, but the variations in design, operating speed, and applications divide the actual function of these devices. There are two primary types of mixers: propeller/paddle and screw (batch and mixer-extruder types). The product quality and brake horsepower are the parameters that can be used to indirectly gauge the performance of a mixer. There are only three major operating concerns for mixers: set-up, incoming feed rate, and product viscosity [14]. The discrete element method (DEM) was used to simulate the mixing of multiple components contained in a typical commercial whey protein mixture [15]. An effective non-sampling mixing index or the subdomain-based mixing index (SMI) was introduced to assess the mixing levels.