Turbulence affects the movement of fluid on a wall. The movement of fluid occurs when there is increased turbulence resulting in a loss of adequate energy. Research seeks to reduce the energy loss due to friction generated by turbulent flow in walls. Studies were conducted ^[1][2][3][1,2,3] in which the discovery of the mechanism of reducing resistance or turbulent skin friction in moving fluids was made. The discovery involved the existence of different substances that can be used, namely polymer-surfactant agents, bio-biopolymers, and solids such as fibers mixed in the inhibitor reducing solution. However, the initial research did not focus on the solution formed but more on the turbulence mechanism in the fluid when a resistance-reducing solution is added. This research also applies to industries such as the petroleum industry, maritime industry, and shipping. The mechanism referred to in research ^[1][2][3][1,2,3] is that the addition of the solution affects the pressure required to decrease the turbulence that occurs in the working fluid in the paper mill when transporting the macerated paper.

Furthermore, Toms [4] took a closer look at polymer development by adding it to a Newtonian solution, thereby reducing wall shear stress. This effect is known as the Toms effect. The wall shear stress is reduced by 80% when the polymer solution is injected into a Newtonian turbulent flow resulting in a non-Newtonian solution. However, Toms has not fully explained this effect because he only clarifies the phenomenon that occurs. Oldroyd [5] describes the events that occurred very well. The external constraints occur on the pipe wall due to the presence of a laminar sub-layer produced by isotropic matter with a thickness proportional to the molecules’ size in the moving fluid.

In the early days of research regarding drag reducing agents, despite the world being affected by a world war, there was a race to find the most effective way to transfer fluid. Weissenberg [6] changed the inner cylinder on a viscometer to produce steady shear, which was continued by Tom’s research in 1958 [7], which used a poly(methyl) methacrylate. To produce 3% polymer change, which showed a lower Weissenberg effect, the rheology of the temperature dependence of the polymer was reduced. Toms did this by adjusting the composition of the polymer mixed in a pure solvent using the Weissenberg method. The method was also used by [6], utilizing aluminum surfactant solvent to reduce the resistance flow of pipes for fuel.

At the same time, some studies ^[8][9][8,9] found that there are factors that influence low friction in non-Newtonian flow by using sodium carboxymethyl cellulose in water, which led to the development of biopolymers in this drag reducing agent study. Ten years after the development of this research, there was a development for industrial applications. Some researchers ^[10][11][10,11] started using guar gum, a plant polysaccharide, as a drag reducing agent. A more in-depth investigation of the characteristics of surfactant polymers in turbulent flow in viscoelastic fluids was carried out ^[9][12][13][9,12,13] with several properties. The reduction of turbulence is strongly influenced by the ratio of elasticity to the viscous force generated by the polymer. In addition to the military industry, the studies of ^[14][15][14,15] were the first to announce that the best polymer used as a drag reducing agent is poly (ethylene oxide). However, several things must be highlighted by further research [9]. References ^[16][17][16,17] examined the characteristics of the drag reducing agent from the aspect of pressure gradient and flow rate resulting from the turbulent flow of different polymers. This is only an initial aspect of the drag reducing agents that require attention. The quantitative theoretical aspects were finally clarified [18], namely polymer molecular weight, polymer concentration, and increased flow rate, increasing the drag reduction effect.

Notably, research on drag reducing agents has been discussed by several sources. A summary of the progress of these studies can be seen in Table 1. However, several reviews of drag reducing additives do not adequately specify the developments in the last decade. This study aims to develop and examine further developments and possible innovations that can be implemented in the next few years regarding drag reducing additives. The improvements can occur by innovating the solvent’s chemical composition or the percentage of the solution. In addition, we examine the mechanism for reducing the resistance that occurs, which is useful for supporting the reduction of barriers, and suggestions for industries that can implement inventions and innovations in the world of chemical and mechanical engineering. This paper aims for completeness and specificity in its review. The definition of one additive with another is a significant factor because many reviews are still wrong in defining these additives. Then, we examine experimental research on smooth circular pipes; some studies have been excluded as they explore other factors such as duct or bend pipes, sometimes using simulations. These studies are nonetheless mentioned in Table 1. Finally, this study focuses on drag reduction caused by wall shear stress based on the difference in pressure gradient in the pipe. We address the final drag reduction result as the main concern is the final effect of the additives.

Several contributions are made in this manuscript: turbulence skin friction, which is the main reason drag-reducing agents research is conducted, will be explained; we also highlight several aspects of drag-reducing additive research, including variables, straight piping configurations, fluid characteristics that flow, type of fluids, and chemical and mechanical degradation. Different polymers, surfactants, and suspensions will be examined in terms of advantages and disadvantages. Lastly, we distinguish and discuss experimental approaches by debating the effectiveness of each approach, optimization, and suggestions for research that can be developed in the coming years.