If you see the appearance of a foreign product and design and calculate the simulation yourself, you can't apply for a patent.
This product belongs to the prior product, so your design does not have the novelty of patent, that is, no matter whether others apply for a patent or not, you have no right to apply for a patent. Even if you apply, you are authorized (the appearance patent is not verified, so long as the format is ok, you will be authorized), but if there is a patent dispute, your patent will easily be declared invalid.
a patent application is a request made by an inventor, designer or other subject with the right to apply to the patent office for a patent right for an invention or design. According to the Patent Law of China, an application for a patent shall submit an application, specification, claims, abstract, drawings and priority request to the Patent Office. Among them, the attached drawings and the priority request are not both necessary for each application.
but it is beneficial to patent application. In a patent application, the application should be in written form, which mainly contains the following contents: the name of the request, invention or design, the name and identity of the applicant, and the name and identity of the agent.